Gaius

"The heart of old Camelot."

- Agravaine, on Gaius

Gaius is the court physician of Camelot and has been for the last twenty-five years, since the birth of Arthur Pendragon. Additionally, he has a great knowledge of sorcery and the legends associated with it, having studied and practised it for many years before The Great Purge. He is Merlin’s mentor and friend, and one of the few people who knows of his magical secret.

Early Life
When Uther’s wife, Ygraine, could not conceive an heir to the throne of Camelot, Uther struck a bargain with the High Priestess Nimueh which would allow her to conceive. He appeared to have sent Gaius, who was then the court sorcerer and physician, to the Isle of the Blessed to make a request on his behalf. Nimueh used her magic to allow Ygraine to conceive an heir. Unfortunately, Uther was not aware that by using magic to create a life, another life had to be taken in order to protect the natural balance of the world. As a result, Ygraine died at childbirth. On the night of her death, Gaius saw the Questing Beast, a magical creature of the Old Religion and an omen of misfortune. After the loss of his beloved wife, a grief-stricken Uther turned on Nimueh, accusing her of treason and banishing her from Camelot, and began the Great Purge, ordering the execution of hundreds of sorcerers, both good and evil. The Knights of Camelot hunted down and killed everyone who had magic in Camelot.

At the start of the Great Purge, Uther gave Gaius a list of all people who were suspected of using magic to be killed. When Gaius discovered his beloved Alice on the list, he struck her name off, thus giving her time to escape. He himself decided to stop practising magic and to remain in Camelot as the court physician.

During the Great Purge, Uther ordered many people to be drowned, including children who had inherited magic from their parents. Morgause, having inherited her mother Vivienne’s magical powers, was sentenced to death by Uther. Gaius was asked to smuggle her out of Camelot after she was born and give her to the high priestesses of the Old Religion. Uther was led to believe that Morgause had died shortly after her birth.

Julius Borden was a pupil of Gaius, who disappeared during the Great Purge, leaving Gaius in a lot of trouble.

Uther was also keen to rid the world of Dragons and tricked Balinor into summoning Kilgharrah to Camelot. Here he trapped Kilgharrah deep beneath the Castle. Uther still persued the Dragonlord, so Gaius helped Balinor to escape execution and hid Balinor with his friend Hunith.



Merlin’s Mentor
"You have taught me so much. Taught me who I am. Taught me the purpose for my skills. Taught me that magic should only be used for great deeds. But most of all, you have always taught me to do what is right."

- Merlin to Gaius

Gaius is the current guardian of Merlin, who was sent to him by his close friend and sister, Hunith. Hunith feared the repercussions Merlin would face should his powers be discovered by Uther or his men. Upon his arrival, Merlin saved Gaius from falling from a balcony in his room using his powers. Gaius quickly took a liking to the boy and promised to keep his secret about Merlin using magic. (The Dragon's Call)

Gaius acted as a surrogate father and teacher to Merlin. He frequently tried to encourage him in his abilities while, at the same time, advising him to look at the bigger picture such as with the plague in Camelot where Gaius tried to make Merlin see that curing one person can have consequences; subsequently Merlin cured Gwen’s father, resulting in her being accused of witchcraft. Merlin and Gaius managed to find the source of the disease; an Afanc in Camelot’s water supply and after the Afanc was destroyed, Gwen was freed. Gaius showed Uther an eggshell Merlin had found underground. The shell bore the mark of Nimueh. (The Mark of Nimueh)

Uther trusted Gaius’ advice frequently in matters concerning magic, (The Mark of Nimueh, The Poisoned Chalice) although at times, they failed to see eye to eye (Lancelot). When Edwin Muirden manipulated Uther into believing Gaius was no longer capable of his job, Gaius was removed from his post as court physician. Furthermore, Edwin threatened to tell Uther about Merlin practising magic if Gaius told Uther about his own use of magic. It was only after Edwin’s attempt to kill Uther, and Merlin stopping him from attempting to kill Gaius, that he was once again restored to his post.



When Arthur was seriously injured by the Questing Beast, Gaius did everything he could to save the prince and managed to keep him alive long enough for Merlin to go to the Isle of the Blessed to find a cure. Arthur recovered, due to Merlin making a deal, but then Merlin’s mother grew seriously ill. Merlin planned to sacrifice himself to save her but Gaius went instead.

On the Isle of the Blessed, he met Nimueh whom he had known before the Great Purge. Gaius persuaded Nimueh to kill him so that both Merlin and his mother could live. It seemed that Gaius actually did die but Merlin arrived and, enraged by the death of his friend and mentor, slew Nimueh. In killing Nimueh, Merlin restored balance to the world, mastering the power of life and death and reviving Gaius.

Gaius was later arrested for sorcery when Aredian, a witchfinder, accused Merlin of using magic and he took the blame. Gaius was locked in the dungeon and was tortured and interrogated by Aredian until he was forced to confess in order to prevent Aredian from killing Merlin and Morgana along with him.Aredian betrayed him and intended to have Merlin and Morgana executed as well. Fortunately, Merlin was able to uncover Aredian’s treachery and Gaius was freed, giving Uther some very harsh words on his views of magic afterwards.

Gaius was frequently seen advising Merlin or assisting him wherever he could. It was Gaius who told Merlin about his father Balinor who was the last living Dragonlord. Gaius helped Balinor escape from Camelot when he was hunted by Uther. He was seen saving as many lives as he could during the Great Dragons assault on Camelot and later comforted Merlin about Balinor’s death telling Merlin, "you've still got me."

Possessed by a Goblin
"Believe me, Merlin, goblins will stop at nothing to get their hands on the one thing they value above all others: gold."

- Gaius to Merlin

When Merlin accidentally released a Goblin, the Goblin possessed Gaius. The Goblin Gaius had a craving for gold and was very manipulative, spreading rumours about fake illnesses so he could sell 'cures' to them. A few of these had side effects - namely, the cures given to Gwen (for a fake illness), Morgana (for her nightmares, as the goblin had stolen her gold healing bracelet) and Uther (for a curse placed by the Goblin, causing him to go bald) included excessive flatulence. When Merlin found out about the Goblin, he revealed his magic. The Goblin then revealed Merlin’s magic to the court, forging evidence with a magic book from a hidden section of the library. Despite Merlin’s original claims of Gaius’ possession being ignored, Arthur grew suspicious of Gaius’ behaviour. He tricked the Goblin into saying he would be glad to see Merlin hang, and silently threatened to either kill or turn him in. In retaliation, Gaius partially turned Arthur into a donkey, giving him donkey ears and a donkey voice. Merlin and Gwen later poisoned Gaius to get the Goblin out of his body but managed to give him an antidote before he died. Gaius then told Uther that he was possessed and that Merlin was innocent. However, this was only half true as Merlin was the one who released the Goblin in the first place.

Gaius’ lover


Later Gaius’ lover, Alice, returned to Camelot under the influence of a Manticore. Gaius was delighted to see her and they worked together just as they had before the Great Purge. Gaius revealed to Merlin that he was in love with Alice and would have married her if not for the Great Purge. When Merlin discovered Alice was in league with a Manticore, Gaius refused to believe him. Alice poisoned Uther, forcing Gaius to realise that she had betrayed him, albeit unintentionally; the Manticore had been too strong for Alice to control. Despite this Gaius remained in love with Alice. He and Merlin managed to destroy the Manticore when Gaius used magic to blow up the box that allowed the Manticore to come from its own world into theirs.

Gaius tried to persuade Uther not to have Alice executed, protesting that she had not been able to control herself because of the Manticore. Uther sentenced Alice to death and Gaius visited her in the dungeon and told her that he loved her. Gaius helped Alice escape from Camelot just as he had twenty years earlier. Merlin noted that he could have gone with her but Gaius replied by saying that if he left there would be nobody to look after the young warlock.

Morgana’s Reign
"Camelot needs us both!"

- Merlin to Gaius

Gaius was the only known person in Camelot, apart from Elyan, who was able to escape Morgause’s immortal warriors unscathed. He was hiding in a cupboard when Merlin and Arthur returned from their failed mission to retrieve the Cup of Life. Merlin and Arthur’s friends, Elyan and Gwaine took Gaius into the safety of the forest while Merlin and Arthur went to find Uther, Guinevere and any other survivors of the assault.



Gaius hid in the woods with Arthur, Merlin, Elyan and Gwaine. Guinevere and Sir Leon met them, having escaped from Camelot and they were soon joined by Lancelot and Percival. Gaius was present when Arthur uncovered the Round Table and knighted Gwaine, Elyan, Percival and Lancelot. Arthur requested that he and Gwen stay behind while they attempted to infiltrate Camelot. Gaius disobeyed the prince and arrived in Camelot in time to stop Morgause from killing Merlin, blasting her with a powerful spell and giving Merlin a chance to smash her against a pillar, wounding and perhaps indirectly being the cause of her death (The Darkest Hour). Then Merlin used Excalibur to empty the Cup of Life and deprive the sisters of their immortal army. (The Coming of Arthur)

The Dorocha’s Attack
"It was on the stroke of midnight of Samhain's Eve, the very moment when the veil between the worlds is at its thinnest. It cannot be a coincidence."

- Gaius to Merlin

When Morgana attempted to take revenge on Camelot again by summoning creatures known as the Dorocha, Gaius told Arthur that the only way to defeat them would be to make a sacrifice in the Isle of the Blessed. Arthur then planned to sacrifice himself despite being the future king. Merlin, who was unable to forsake his destiny to protect Arthur, told Gaius that he would sacrifice himself in Arthur’s place despite Gaius telling him not to go.

Meanwhile, Arthur’s uncle Agravaine took charge of the kingdom in Arthur’s absence and had the city gates closed to prevent food running out. Gaius angrily confronted Agravaine and Gwen persuaded him to reopen the gates. Gaius then suspected that Agravaine was loyal to Morgana and later discovered that Gwen had been knocked unconscious by Morgana before curing her. After Merlin, Arthur and the others returned to Camelot when Lancelot sacrificed himself to defeat the Dorocha, he and Merlin learned that Morgana was aware of Merlin’s identity as Emrys. After telling Merlin of his suspicions of Agravaine, he warned Merlin that Morgana should never learn that he has magic and that he is Emrys. (The Darkest Hour)

Arthur’s Coronation & Merlin Kidnapped
When Uther was mortally wounded by an assassin, Arthur begged Gaius to save him but Gaius told him that because Uther’s heart was bleeding, he could not be cured and would only live for a few days. Arthur, however, planned to save Uther with magic and Merlin saw this as an opportunity to convince Arthur to return magic back to Camelot by returning to his old man (Dragoon the Great) disguise. However Agravaine told Morgana of Arthur’s plans and she made him put a necklace she enchanted around Uther’s neck and repel healing magic. When the disguised Merlin used a healing spell on Uther, the necklace repeled it and Uther died.

Gaius later showed the necklace to Merlin and he realised that it was Morgana. As Arthur mourned Uther’s death, Merlin blamed himself for his death and worried that Arthur would never learn that he is a sorcerer as Arthur’s heart was again hardened against magic. Gaius reassured Merlin that he was not to blame for Uther’s death and that Arthur would soon learn that Merlin is a sorcerer. Gaius later watched as Arthur was crowned King of Camelot. (The Wicked Day)

After Merlin was kidnapped by mercenaries and taken to Morgana, Gaius expressed great concern and was told by Arthur that he would not rest until Merlin was recovered. When Merlin was found by Arthur and Gwaine, Gaius was relieved by his return, unaware that he had previously been kept hostage by Morgana and was now brainwashed into trying to kill Arthur.Gaius grew suspicious of Merlin’s abrupt and rude behaviour and eventually concluded with Gwen that he was being controlled by a snake known as the Fomorroh. Gaius attempts to remove the snake, only to find that it had grown back and the only way to truly kill it is to murder the mother snake. Merlin, now under free will, dressed up as Dragoon and returned to Morgana’s hovel where he successfully burned the rest of the Fomorroh. He later faced Arthur’s wrath after Gaius claimed that he spent time in the tavern.

Kidnapped
"Emrys is a name by which he is known to the druids, but to me...I know him by a different name."

- Gaius to Alator

Gaius was later suspected of sorcery because Agravaine framed him, claiming that he had been partially responsible for Uther’s death since he had revealed where "Dragoon the Great" lived. Gaius appeared to have fled as there was a horse missing from the stables but in reality he had been kidnapped by Alator, an ally of Morgana and taken to a cave where he met Morgana. He showed no fear of her and simply told her to get on with it. Alator used a ring of fire to trap him, which Gaius put out with a counterspell. Alator was slightly surprised by quickly reactivated the fire and started to use mental torture to force Gaius to tell him the true identity of Emrys. Gaius resisted the torture for a long time but eventually Alator overpowered him and forced him to reveal that Emrys was actually Merlin. Shortly after this he was nearly murdered by Agravaine but thanks to the arrival of Gwaine, Agravaine was forced to pretend that he'd merely been making sure that Gaius was still breathing and the two men brought Gaius back to Camelot. Meanwhile Alator protected Merlin from Morgana, having realised that Merlin was Emrys, and Merlin returned to Camelot. When Merlin was reunited with his mentor, Gaius told him he was ashamed to have revealed his secret but Merlin reassured him by telling him about Alator’s true loyalties. Arthur then arrived and apologised to Gaius for suspecting him of sorcery. Gaius admitted to Arthur that he had lied about not knowing the man whom Arthur assumed had killed Uther and explained to him that Merlin (who was disguised as Dragoon at the time) truly had done his best to save Uther. Because of this, Arthur’s hatred towards magic decreased slightly. (The Secret Sharer)

Lamia Rampage
"Merlin is right. This is no ordinary illness. There is sorcery at work here."

- Gaius to John Howden

When Gaius is asked to go to Longstead to investigate a strange illness he has to decline. The sweating sickness is sweaping through Camelot and poor Gaius is up to his elbows in work. Merlin is sent instead as Gaius never doubts that his ward is a skilled physian. When Merlin and the others fail to return Gaius accompanies Agravaine and Arthur to Longstead to investigate. It soon becomes crystal clear to Gaius that a Lamia is on the loose. After Lamia is killed Gaius is able to cure all those afflicted by the creature. (Lamia)

Lancelot's Return
"This man's a shadow of his former self. A shadow with ill intent."

- Gaius to Merlin

When Lancelot suddenly appears Gaius is immediately suspiscious. He helps Merlin in figuring out that Lancelot is now a shade with an evil agenda. The court physician also correctly guesses that Morgana is behind it all because she felt threatened by Guinevere. (Lancelot Du Lac)

Arthur's Dark Past
"Anyone who disturbs a resting place risks releasing the spirit. Merlin, you must promise me you'll never return to that place."

- Gaius to Merlin

When Merlin tells him of an eerie shrine deep in the forrest Gaius warns that the place is haunted and hopes that no one was foolish enough to disturb the restless spirit. It soon becomes clear that Elyan did just that and is now tormented by the phantom. After investigating the shrine for himself Gaius tells Arthur that the spirit is that of a druid boy. He suspects that it is one of the many child sorcerers that Uther had murdered. According to Gaius the culprit must show true remorce for the soul to able to move on to the afterlife. This seems unlikely as Uther is now dead. Gaius was in fact unaware that it was Arthur's fault that the young boy died. (A Herald of the New Age)

Princess Mithian
Gaius notices that Merlin seems sad. His ward explains that he knows that Arthur is destined to marry Guinevere but asks himself if he should nudge things in the right direction. Gaius cautions Merlin against arrogance. Their discussion is cut short when Sir Leons comes in. Agravaine has summoned Gaius to examine a mangled body (that Agravaine himself put there) found at the bottom of one of Camelot's towers.The physician immediately deduces that the man died of a broken neck. Still Gaius is puzzeled as to why the man has no other broken bones. Later that day we find Gaius examining the letter found on the dead man's body proving that he turned traitor for King Odin. He knows that something is off with the correspondence but can't quite put his finger on it. Gaius is so distraced that he doesn't pay heed to Merlin's rant about Arthur and Mithian.

Morgana's Second Conquest Of Camelot
"It seems your victory is short-lived Morgana"

- Gaius to Morgana

Like everyone else Gaius is caught completely off guard when Morgana and Helios invade Camelot. The physician realizes that Merlin's worst fears have come true. Gaius takes care of the wounded as best he can during Morgana's attack.Gaius agrees with Merlin that Arthur should be enchanted to force him to leave the city. He refuses to follow his ward however saying that he will slow Merlin down. Gaius is soon confronted by Morgana herself. Locked in the dungeons Gaius immediately sees that Elyan has been tortured by use of a Naithair serpent. Soon Elyan recovers, but it is revealed that Gaius, Gwaine and Elyan aren't receiving any food as punishment for having fought agaisnt Morgana's troops. Gwaine demands that Morgana give them there rations, and in return is forced to fight, weak and ragged, for Morgana's entertainment to earn food. In part two of The Sword in the Stone, Guais has grown very weak and ill from starvation much more rapidly than the two younger men. Gwaine and Elyan are concerned for his health. Gwaine is continuing to fight, and his health gets worse and worse each battle. When Elyan tells Gauis to eat the food that Gwaine won, Gauis refuses, saying that Gwaine will need all of the strenghth he can get. Elyan leaves the loaf of bread in Gauis's hand. When Guais and the others are rescued, Gauis is in a very critical condition, and Gwaine can hardlly stand up, but soon the two men are cared for, and attend Arther and Gwen's wedding.

Queen Guinevere
After being starved for so long during Morgana's rule Gaius is near death. The physician goes on to refuse any food Gwaine has scraped together. Gaius believes he isn't long for this world and that his fellow prisoners have a better chance at survival as they are still young. Luckily for Gaius, Merlin and Arthur succesfully retake Camelot and they get to him just in time. When Guinevere is crowned queen a fully recovered Gaius is seen among the guests, proudly proclaiming: 'Long Live The Queen!'.

Personality
Gaius is sensible and believes in thinking rationally about things rather than rushing to decisions. He was loyal to Uther despite the methods the king used to deal with sorcerers and the use of magic. The only person who Gaius valued more was Merlin, whom he came to love like a son (A Remedy to Cure All Ills). Gaius also seems to have known the Great Dragon for at least twenty years (A Remedy to Cure All Ills) and trusts his advice, but when Merlin told him that the Great Dragon cared only for himself, he did not protest, suggesting he too had reason to believe that beforehand. But he also knows that there are times when the Dragon’s assistance is needed.



Gaius also possesses a dry sense of humour and is one of the few people in Camelot who was brave enough to stand up to Uther Pendragon (The Witchfinder). Agravaine noted that Gaius was loyal and stubborn, and Merlin once called him a "stubborn old goat". He is also strong willed and was able to resist Alator’s mental torture for quite a long time, but eventually the more powerful sorcerer overpowered him (The Secret Sharer). He frequently scolded Merlin about using magic but knew when using magic was necessary. Gaius was willing to give his life for Merlin which was shown in two episodes.

Although Gaius is a good person, he had a habit of keeping secrets, particularly from Uther Pendragon, even though he revealed Merlin's true identity to Alator when tortured. However Gaius only kept secrets because he, unlike Uther, knew that magic could be used for good and he was still loyal to the king and never considered turning against him even after Uther nearly had him executed. Gaius would also risk the wrath of the king if he felt it was necessary and helped Balinor and Alice escape from Camelot, risking execution by doing so. He is also cunning and he was the only known person in Camelot, apart from Elyan, who escaped Morgause’s immortal army unscathed. Gaius always looks at the bigger picture when he needs to break a promise, knowing that Uther had to know the truth about Morgause in order to ensure the safety of Arthur and Camelot and also knowing that Agravaine must not find out who Emrys really was, for the sake of the whole kingdom.

Many years before the series began, Gaius helped Balinor escape from Camelot despite the fact that if he'd been discovered helping the Dragonlord he would have been executed. Because he helped Balinor, the Dragonlord felt he owed Gaius a debt that he had to repay, referring to him as a good man. Gaius is also extremely dedicated to his job as Court Physician and would never give up on a patient no matter how serious the illness or injury.

Merlin
"Merlin, you are the only thing I care about in all this world. I would give my life for you without a thought"

- Gaius to Merlin Gaius is very close to Merlin, thinking of him as the son he never had. He was willing to give his life for Merlin which was proven on at least two occasions (Le Morte d'Arthur, The Witchfinder). Gaius is very proud of Merlin but sometimes scolded him about using magic, unless it was for good reason. He often provides Merlin with advice and comfort and was seen hugging him on several occasions. In return, Merlin loves Gaius like a father. They also joke with each other at times.



When Gaius was possessed by a Goblin, Merlin poisoned him to get the Goblin out of his body but he and Gwen managed to give him an antidote before he died. Gaius felt no resentment towards Merlin for poisoning him as he understood that it was the only way to get the Goblin out of his body and their relationship remained as close as ever. While waiting for Gaius to recover from the poison, Merlin called him a "stubborn old goat".

Later when Gaius’ lover Alice returned to Camelot, he and Merlin had a falling out because Gaius refused to believe that Alice was being controlled by a Manticore. When Merlin brought guards to arrest Alice and told Gaius that it was either him or her, Gaius responded by telling him that it was not his choice to make. However, he still loved Merlin and after helping Alice escape Camelot, he stayed behind to look after him. Their relationship quickly returned to normal after Alice escaped. When Merlin was attacked by Morgause, Gaius attacked the sorceress himself in order to protect him and by working together, he and Merlin managed to defeat Morgause.

Uther
"Gaius, once again you've saved my life, you've always served me well"

- Uther to Gaius

Gaius is a good servant and loyal friend to Uther despite Uther’s hatred of magic. He has saved Uther’s life many times through his skills as a physician. However after being wrongly accused of magic, a furious Uther ordered him to be put to death but Gaius was later proven innocent. When Uther tried to apologise for Gaius’ suffering at the hands of the Witchfinder, Aredian, Gaius told him that it was not Aredian who was responsible for his suffering, but Uther himself. He also told him that he wasn't the only one who was wrongly accused of using magic and that not all had been as lucky as him. Gaius was one of the few people who could speak to Uther however he wanted and though he was usually polite to the king he would sometimes stand up to him and point out his mistakes. After discovering Gaius was innocent, Uther’s trust in him strengthened so much that he even gave him permission to use magic to heal Morgana after she fell down a flight of stairs. Though he was very loyal to the king, Gaius often had to keep secrets from Uther, most notably the fact that he was hiding a sorcerer right under the kings nose. Despite his habit of keeping secrets, Uther trusted Gaius and valued his advice and friendship. When Uther was broken by Morgana’s betrayal, Gaius pitied him and feared that Uther would not recover but expressed that it gave Uther peace. After Uther’s death, Gaius expressed to Arthur that he was sorry that he died but told Merlin that Uther’s spirit had already died when Morgana betrayed him.

Morgana
"I know I can trust you Gaius"

- Morgana to Gaius Morgana often went to Gaius for potions that were supposed to help her with her nightmares, which were sometimes effective but more often not. Morgana admitted to Aredian that her dreams got worse when Gaius started treating them, though she insisted that this was just a coincidence. She initially trusted Gaius a great deal, even though she told Aredian that she had no idea what he'd put in the potions, because he took care of her and his draughts were the only thing that let her get any sleep. Gaius seemed very fond of Morgana, often calling her "my child" in a grandfatherly tone, but Gaius firmly maintained that Morgana was better off ignorant about her powers, often lying to her about the importance of her dreams and powers in hopes of protecting her from Uther's hatred of magic. He believed that the draughts, which essentially drugged her so that she could not dream, were the best treatment, and was angry when Merlin argued with him about it.

Despite his fondness for Morgana, after the sleeping plague he was quick to believe Morgana had allied herself with Morgause, despite the fact that this was not yet true. He told Merlin he did the right thing by poisoning her, and that Morgana had chosen to use her gifts for evil, despite the fact that at this point she had been nothing more than an unknowing vessel for Morgause’s scheming. Gaius’ former good opinion of Morgana was stripped away and he was highly suspicious of her when she returned. Although he acted as if nothing had changed, Gaius helped Merlin work to thwart her plots time and time again, and when he was possessed by a goblin he told her that her heart was full of darkness. Although Gaius was not initially an object of her hatred, he finally became one of her targets once she suspected that he knew of Emrys, leading to his kidnap. Morgana showed none of her former respect and affection for Gaius and was happy to firstly torture him to extract information, then later leave him deteriorating in a cell without sufficient food.

Arthur
"I love you far too much ever to betray you"

- Gaius to Arthur Gaius and Arthur shared a mutual respect for each other and Arthur knew Gaius well enough to realise when he was being possessed by a goblin. (Goblin's Gold) At first, Arthur didn't believe that Gaius was, or ever had been, a sorcerer. Gaius later told Arthur that he loved him and Arthur thought of Gaius as a member of his own family having known him ever since he was born. (The Secret Sharer) Whe necessary, Gaius did not hesitate to lie or bend the truth to Arthur, in order to protect him and maintain his position on the crown. Gaius was not afraid to speak up to Arthur, and like Merlin, addressed him by his name alone on many occasions and not his title.

Guinevere
"I don't know who else I can talk to"

- Gwen to Gaius upon finding out Morgana was using dark magic Gaius was friends with Guinevere who went to him when she discovered her father was dying. Gwen also gave him a kiss on the cheek when he was about to leave Camelot (A Remedy to Cure All Ills). Gaius eventually discovered Guinevere’s secret relationship with Arthur Pendragon; he approved and gave Gwen new hope for the relationship (The Last Dragonlord). Gwen helped save Gaius’ life on two occasions, first when he was about to be burned at the stake by Aredian and later when he was dying from poison after being possessed by a goblin. She also went to Gaius and told him that she had discovered Morgana using magic.

Hunith
"My dear Gaius, I turn to you for I feel lost and alone and don't know who to trust"

- Hunith to Gaius Gaius seems to have a very good relationship with Hunith, Merlin’s mother. She entrusted him the training and well being of her son by sending him to live with Gaius. He helped Hunith by hiding her lover, the Dragonlord Balinor from the wrath of Uther during the Great Purge. Hunith also sought help from Gaius when Nimueh almost killed her. Gaius was willing to give his life in order to save Hunith, which proves the close friendship that Hunith and Gaius have.

Kilgharrah
"How old a man can grow and yet change so little"

- Kilgharrah on Gaius Gaius has known Kilgharrah for at least twenty years and on at least one occasion, he visited the Dragon for advice. Gaius respected Kilgharrah’s power and wisdom but they weren't friends and Gaius was probably aware that Kilgharrah was desperate for his freedom.

Kilgharrah cared little for Gaius, stating to Merlin that he has no place in his destiny and the "old man’s" time is over anyway, when Gaius went to the Isle of the Blessed to sacrifice himself for Merlin and Hunith. Kilgharrah even told Gaius all he is good at doing is standing by and watching, implying little regard for his importance. Kilgharrah’s views of things often clashed with Gaius’, for example in the episode Aithusa; while Gaius wanted the dragon egg untouched as he said it should be Kilgharrah begged Merlin to obtain the egg. Gaius later accepted this, though, and even held the egg.

Aredian
At some point in the past, Gaius met the Witchfinder Aredian. He disliked Aredian but respected and feared his abilities as a Witchfinder and claimed he was a force to be reckoned with. Gaius greeted Aredian politely when they met but it was obvious that he disliked the Witchfinder. When Gaius was arrested for sorcery Aredian acted as his interrogator. However, Gaius attempted to make a deal with Aredian to prevent Merlin and Morgana from being executed along with him. Along with Merlin he made fun of Aredian after he died, doing an imitation of him coughing up a toad.

Alice
At some point before the Great Purge, Gaius fell in love with Alice and they were even engaged to be married at one point. However, the Great Purge forced them to separate and they didn't see each other for approximately twenty years. They continued their romance when she returned to Camelot. However Gaius, blinded by love, was unable to realise that Alice was being controlled by a Manticore. When he did realise however, he continued to love Alice and Alice genuinely loved Gaius in return despite the influence of the Manticore. Gaius helped Alice escape from Camelot just as he had twenty years earlier. Merlin noted that Gaius could have left with her but Gaius had decided to stay in order to look after Merlin.

Balinor
Gaius was a friend of Merlin’s father, Balinor and helped him escape from Camelot when Uther ordered the Dragon Lord’s execution, risking being executed himself by doing so. Balinor was grateful to Gaius for saving his life and called him a good man. Gaius indirectly influenced Balinor to return to Camelot to save Camelot from Kilgharrah since Balinor felt he had to repay Gaius to saving him all those years ago.

Morgause
During The Great Purge Gaius smuggled Morgause out of Camelot and handed her over to the High Priestesses of the Old Religion, where she was trained from very young to become the powerful sorcerer she was in Series 2 and 3. When Morgause later returned to Camelot in order to seduce Arthur into coming to her castle so she could turn him against Uther, Gaius tended to her wounds. Morgause told Gaius she was in Camelot when she was a baby and Gaius recognised her wrist bracelet, which he later used as non-physical evidence to inform Uther of where Arthur was going and what Morgause intended on doing with him. Gaius met Morgause again in the Series 3 finale where he used a spell to hurl her across the room as she was about to kill Merlin. As she stood up to strike back at Gaius, Merlin attacked her, along with Gaius who went for another blow, and their combined hits knocked Morgause unconscious against a pillar. Whether Morgause previously knew of Gaius’ magical abilities is unknown, but she possibly did or expected him to have some magical knowledge as Morgana did not seem to comment on it when she met Gaius in Series 4 following the events.

Nimueh
Gaius knew Nimueh well as they practised magic together before the Great Purge. However when Uther Pendragon outlawed magic, Gaius remained loyal to Uther, while Nimueh was determined to take revenge on Uther. Nimueh believed that Gaius betrayed her and his kind by his loyalty to Uther, and called him a traiter when he confronted her on the Isle of the Blessed. Despite her resentment for Gaius, she agreed to sacrifice his life when he wanted to save the life of Merlin's mother, Hunith, which resulted in her death at the hands of Merlin.

Abilities
Gaius believed that basic problems should be solved by science. He was an excellent physician which has been proven on many occasions. However, Edwin Muirden claimed his methods were "outdated", though this was possibly a lie to give Uther reason to appoint him as Court physician instead.

Gaius had a very broad theoretical knowledge of magic but when he used magic in Season 1, he initially forgot the words (The Poisoned Chalice) or mispronounced the words (A Remedy to Cure All Ills). This shows that his magical skills have greatly decreased due to the many years he went without practice. The only successful time Gaius used magic in Season 1 was when he created an antidote for Merlin when he got poisoned by Nimueh.

However Gaius’ magical skills have clearly improved as the series went on. He used fairly strong magic when the goblin took over his body, though this was probably the goblins magic not his own (Goblin's Gold). He later used magic to destroy a box that contained a Manticore, after luring the Manticore out of the box though he had to try three times before he succeeded. However it required powerful magic to destroy a Manticore’s box, showing that Gaius had indeed grown stronger in magic. Gaius was even able to successfully attack Morgause, who was an extremely powerful sorceress, in order to protect Merlin, hitting her with a spell which sent her flying and stunning her long enough for Merlin to seriously injure and perhaps kill her, by throwing her into a pillar (Although the fact that he caught her off guard while she was focused on Merlin may have contributed to his victory). Recently, Gaius was captured by Alator, a powerful warrior and sorcerer. Though he was eventually defeated, he resisted Alator's mental torture for quite a while though it is unclear if he did this through magic or willpower. Gaius even magically put out the enchanted ring of fire keeping him captive although it was quickly reactivated by Alator. This shows that he is still a capable sorcerer.

Gaius also had a talent for keeping secrets; being able to hide a sorcerer, Merlin, right under the nose of Uther Pendragon, smuggle Morgause out of Camelot without Uther knowing until many years later and help Balinor and Alice escape Camelot (the latter individual twice). Gaius was also capable of hiding and avoiding attacks, because he was the only person, apart from Elyan, to escape capture when an immortal army invaded Camelot. (The Coming of Arthur)

Behind the scenes

 * Gaius was the first name of Julius Caesar. It is a Roman praenomen but the odds of someone in fifth or sixth century England at the time the series presumably takes place, when the Western Roman Empire had fallen in the fifth, are unlikely at best.
 * Gaius is perhaps based on Blaise, who according to some sources such as Robert de Boron’s epic poem Merlin, was Merlin’s mentor.
 * In Secrets and Magic: Gaius is twice referred as Merlin’s uncle, Richard Wilson also said this in an interview, however this relationship has never been mentioned in the series.
 * Richard Wilson plays a similar character, Father Simeon, in Shine Limited's shorter-lived other Saturday-night drama, Demons. Both are experts on the prominent theme of their series, Gaius is an expert on magic, and Simeon is an expert on supernatural creatures.