A potion, a consumable medicine or poison is usually made by a sorcerer, warlock, witch, elf or faerie and has magical properties. It might be used either to heal, enchant or poison people.
The known potions that have been used in the series are:
- Gaius' magical antidote, made from the Mortaeus flowers. He chanted this spell on it: "Seópan ærest wearð feasceaft funden. Denum æfter dom. 'Dreamleas gebad he gewann langsum" (The Poisoned Chalice).
- The troll's potion. It was made by Jonas for his mistress. The troll had to continually drink it to take on the form of the Lady Catrina of Tregor. According to Gaius, this is really powerful magic to physically change her like that, and this is futher supported by the fact that her image in a mirror didn't reveal her true appearance, while reflections are a normal weakness to this kind of magic. After Merlin tried to cast the Spell of Revelation on Catrina, she had to drink her potion again to fully contrast the pain caused by this spell. The court physician made a potion that looked and tasted the same. Without the troll's magic, it had no effect and Catrina's true form was exposed. It was made of rat's guts, toad paste (two toads ground up), horse dung, crushed sheep's eyeball, pond scum, three wolf spiders and a dash of sheep's brain (Beauty and the Beast).
- Trickler's love potion. He made it one with a lock of hair from Arthur, then with one from Vivian to make them fall in love. According to Merlin, there are over 636 love spells and over 150 of them involve a lock of hair. Love potions are very powerful, for they influence the greatest force of all, which is love. Trickler chanted a spell ("Ales, læfe he híe þonne he áwæcaþ. Biþ his hyht þæt he her seón mote ána oftíe þonne ealle mán") on the potion, while he was heating it on a candle (which he also lit with magic) and weaving over it the lock of hair. He then put this potion on Arthur's and Vivian's eyes while they were sleeping (Sweet Dreams).
- Morgause's potion to enchant the mandrake root. It was a thick, dense, black liquid similar to dark mud that she had prepared in a big cauldron. She threw a handkerchief, which had Uther's tears on it, with the root itself in it, that sank in the potion. She chanted this spell: "Mid þæm wundorcræft þæs ealdan æwþ ic þe hate nime Utheres wopdropan ond þa gemengan mid his blod. Sy he under wittig ond deofol seocnes his heorte afylþ". According to the spell's translation, Morgause said that she was mixing Uther's tears with his blood: this may indicate that the potion contained blood. Furthermore, when Morgana hid the mandrake root under her cloak and some of the potion dripped from it, a guard thought she was bleeding. Every night Morgana had to return to Morgause's cave and recover the Mandrake root with the potion (The Tears of Uther Pendragon: Part One).
- The Goblin's potions. He created many of them and sold them to the citizens of Camelot to earn gold coins. The one he gave to Morgana, Uther and Gwen (a sleeping draught that had been enchanted) caused them to suffer from flatulence. The Goblin also used another potion to cure Uther of his baldness (which he had caused, too). Another potion, that Gaius had secretly added to a flagon of ale which he then had served to Sir Leon and other knights, caused the man's face to be completely covered in boils. To force Sir Leon to pay a fortune in gold coins, the Goblin said that the infection had no cure and that the itching would become so unbearable and severe that the patient would be driven to madness (Goblin's Gold).
- A potion created long ago by the Witches of Meredor that can force a faerie out of a changeling. Gaius prepared it to save Princess Elena, but in the beginning he didn't know how to make it, not knowing what a lot of the potion's ingredients were. According to Gaius, the Witches of Meredor were the worst recipe writers he'd known. One of the potion's ingredients was the stamen of the dropwort flower, rearer than a four-leaf clover. They grow in a boggy and marshy terrain (The Changeling).
- Alice's remedy. It was a dust that sparkled with magical power and it was given to the innkeeper's wife for her dying husband. Thanks to it and to a Sorcerer's chime, the man was saved (Love in the Time of Dragons).
- Gaius's prescription for Uther. It was given to him for an old battle wound and made of hemlock, nightshade and valerian. The king had to take it daily. Alice, under the manticore's power, decided to add to it the creature's venom (Love in the Time of Dragons).
- The potion Merlin used when he cast an ageing spell on himself. He had prepared an unknown blue powder that he threw in a cauldron. The spell he chanted caused the powder to explode and the white smoke that rose to his face made him grow older (Queen of Hearts).
- Gaius' antidote for ageing spells. He found it in the Book of Gallah and he said it would have taken a long time to make it. This was indeed a difficult potion to prepare and it took Gaius an entire night make it. The readable instructions that were shown on a page of the Book of Gallah were: "No other aging reversal antidote exists other than by using pure magic. Unless you have some sorcery skills then you will not be able to carry out the above antidote to reverse the spell that has been performed in order to make a person look older. Once you have gathered your ingredients together with a small drop of water and vinegar, you must bind the ingredients with magic. This may take up to three or more hours and this process cannot be rushed. Once the ingredients are bound, you will then heat the liquid at a graduate rate. The flame must be orange and not blue when..." (Queen of Hearts).
- Morgause's tracking potion. It was a white dust that Morgana secretly added to Gwen's wine. When Morgause chanted the spell "Beo þu leohte bewunden", the path that the maid had followed was illuminated. After a certain time the potion began to lose its power and Morgause, who had followed Gwen with her men, had to chant another spell ("Scin scire") to reveal Gwen's way (The Coming of Arthur: Part Two).
- The potion Merlin, disguised as "Dragoon the Great", used to try to cure Uther. It was invented by Gwillem of Cambria who was, according to Gaius, mad as a coot but one of the best healers of all. Gaius told him to use only four drops, because any more could have been dangerous. After making Uther drink the potion, Merlin chanted a healing spell (The Wicked Day).
- Morgana was seen preparing some potions on the table of her hovel when Agravaine burst in, telling her that he had failed to steal the plans to the siege tunnels under Camelot (The Hunter's Heart).
- When Gaius informed King Arthur that the only way to banish Uther's ghost from this world was to use the Horn of Cathbhadh again and reopen the Veil between the world of the living and the Spirit world, he prepared a potion that would have allowed Arthur and Merlin to see the dead king in his spirit form. In Arthur's chambers, the old physician gave the two young men one little vial of green potion each, but when he declared that he wasn't entirely sure about the elixir's effects, Arthur waited for Merlin to drink the potion first, to see if it wasn't poisonous. Merlin drank the green liquid, but didn't inform Arthur of his foul taste, which made the King feel sick (The Death Song of Uther Pendragon).
- Morgana went to an apothecary named Sindri, who lived in a hut in the woods outside Camelot. She asked him for a tincture with the power not just to kill, but to do it slowly and the utmost pain. The sorceress bought, for an handsome price, a vial of valerian, two drops of which could render the victim unconscious, and another of henbane, which, if a single drop would be administered through the ear, could give a prolonged and unpleasant death. She gave them to Gwen and the Queen, who had been turned into Morgana's ally by dark magic, poisoned the King; the sweating, the corruption of the skin and the traces of tincture around the ear allowed Gaius to recognize the poison, but only Merlin's magic was able to save Arthur from certain death (A Lesson in Vengeance).
- After having knocked Merlin unconscious with a stunning spell, Morgana uncorked a small vial and poured a black liquid down her enemy's throat; according to her, the agony caused by this poison would make Merlin gladly welcome death when it came. When the young warlock came round, he failed to heal himself with magic. He would have died if it hadn't been for Daegal who, regretting his past actions, fetched rue, a plant with yellow flowers and feathery leaves, milfoil and yarrow for him, ground them into a tincture and had him drink it. Thanks to this antidote, Emrys recovered (The Hollow Queen).
- To take Queen Guinevere, who had fallen prey to Morgana's dark magic, to the Cauldron of Arianrhod, whose waters could heal her from the Teine Diaga, Merlin administered her Belladonna, a powerful and dangerous drug, generally used for the badly wounded. The patient is rendered into a deep sleep, which only lasts a few hours; to provide a continuous sleep, two drops of the substance have to be administered every two hours, but for no more than three days, otherwise the body will not tolerate it (With All My Heart).
