Glamour

Glamour is a form of enchantment that enables a witch or a warlock to make themselves (or someone else) adopt the appearance of a different person or animal in the eye of the beholder. It is unknown if this kind of spell counts as true shapeshifting or as mere visual illusion, though it's possible that Gwen's transformation into a deer might have been truly physical since, while her true form was visible in reflection, Arthur and other experienced hunters claimed that her tracks were that of a deer.

However, users of this spell should generally take care to avoid reflective surfaces such as mirrors or water pools, as they reveal one's true shape.

A very powerful form of glamour is an Ageing spell.

Magical illusions
Mary Collins used this enchantment to disguise herself as Lady Helen so that she could take her revenge on Uther Pendragon. To cast this spell she used an amber necklace. The witch was no longer able to hold this spell when Merlin made a chandelier fall on her back (The Dragon's Call).

Anhora, the Keeper of the Unicorns, conjured a powerful illusion to test Arthur Pendragon, shaping through his magic a man named Evan who vanished when Arthur stabbed him. It's possible, however, that Anhora had used magic to disguise himself, as after Arthur let him have the grain, he talked similar to Anhora, and when he disappeared, it was in the same way Anhora used to teleport (The Labyrinth of Gedref).

Gaius, while possessed by a Goblin, cast a glamour on Arthur, who had understood that Merlin was saying the truth about the physician. He partially transformed the Prince into a donkey, giving him the animal's ears and making him bray. The Goblin was powerful enough to cast this spell without an incantation (Goblin's Gold).

Another form of glamour can be put on a person with the aid of a Blood crystal. If ths magical instrument is enchanted ("Þece treowee andwlitan heora fram gesiht eallra!") its wearer will be able to take on the the physical appearance of anyone whose blood the crystal touches. However, the true identity of the owner of the crystal can be seen reflected into the crystal itself. The sorcerer, Cylferth, gave two thugs, Dagr and Ebor, two Blood crystals and they used them to take on the form of Sir Oswald and Sir Ethan to enter a tournament in Camelot and take their revenge against Prince Arthur. After the two thugs were killed in the melee, Gaius removed the crystals from around their necks and the enchantment was broken (Gwaine).

It is possible that Morgause used this enchantment to disguise herself as an old woman so that she could visit Morgana, as her true form could be seen in a mirror. Morgause's spell probably wasn't as powerful as Mary Collins', for only her face was aged (Morgana noticed that her sister's hands were not the ones of an old woman) and she said that the enchantment wouldn't have held for long (The Eye of the Phoenix).

After having slammed Gwen against a tree, knocking her out, Morgana decided to put a glamour on the servant when she heard that a group of hunters, led by Arthur Pendragon, was approaching. She cast a spell on her former friend ("Nu bebiede ic þe þæt þu lætest þine flæsc sclice gelic nysse. Wyrþ deor") and as Gwen's body progressively glowed with a golden light, she was turned into a deer. Arthur, Mithian and the Knights of Camelot quickly reached the animal and were about to kill her. Merlin, who had seen the deer first, was not affected by Morgana's enchantment: the animal's true appearance was reflected in his eyes and he caught a glimpse of Gwen, in her human form, in a puddle. The young warlock deflected Arthur's arrow with his magic, but Gwen was injured by Mithian. That night, when he found the maid and cured her, Morgana's glamour had stopped working (The Hunter's Heart).

Other forms of glamours
It's possible, however, to cast glamours that not only hide someone's appearance but also allow the sorcerer, who must be enough powerful and experienced, or its victim, to become undetectable by reflections.

The troll that took on the form of the Lady Catrina, for example, was able, with the help of her servant Jonas, to create a potion so powerful that her physical form changed completely and her reflection in a mirror couldn't show how she really was. According to Gaius, really powerful magic was needed to make such creature change its form, though this might have been a sarcastic remark about the troll's naturally hideous appearance (Beauty and the Beast).

It's possible that the High Priestess Nimueh used glamours to hide her real appearance. When Gaius informed the King that the true responsible for poisoning the Mercian ceremonial goblets was Nimueh, Uther said that if it had been her, he would have recognise the witch's face. Gaius, however, replied that she was a powerful sorceress, capable of enchanting the eye that beholds her (The Poisoned Chalice).

Shapeshifting
Shapeshifting is the ability to change someone's physical form at will. Different magical creatures are able to do this:
 * A Sidhe can take up a mortal form and body if cursed by other faeries (The Gates of Avalon).


 * A person that has been cursed to become a Bastet transforms herself into a large panther with bat-like wings on the stroke of midnight (The Lady of the Lake).
 * Goblins can shapeshift into small bright balls of light and are able to possess someone while in this form (Goblin's Gold).


 * Pixies can change their appearance from creatures with pink skin, large pointed ears, long noses, dozens of long black warts on their face and plump clawed fingers and disguise themselves as humans (The Changeling).
 * The Lamia could transform from a humanoid girl into a huge beast with many tentacles (Lamia).

Although not precisely shapeshifting, spells have been used in different occasions to alter the essence of objects:
 * Anhora's magic, when the curse of the unicorn was raised by Arthur, caused all the crops and livestock in the entire kingdom to die. The curse then transformed Camelot's water supply into sand and made what little food they had left rot (The Labyrinth of Gedref).
 * By Merlin, with the incantation “Gréot gecumen lecan. Gecumen gé drý wæter”, who tried to work his magic on a bucket of sand and change it back into water. However, Anhora’s and the cure’s magic was more powerful than his (The Labyrinth of Gedref).
 * By Merlin, with the incantation "Hlyste min níehst bebod", to create many copies of the amulet of enchantment Aredian himself had hidden in Gaius' chambers to accuse the physician of practicing sorcery, along with the eye drops of Belladonna. By conjuring the amulets in the Witchfinder's cupboard, the young warlock was able to make Uther believe that Aredian himself was a sorcerer (The Witchfinder).
 * Trickler, to amaze the court during the Peace of the Five Kingdoms, used real magic to make many butterflies appear from thin air (Sweet Dreams).
 * Non-verbally, by Grettir, to turn Gwaine's sword into a flower and back again when he was threatened by the knight (The Eye of the Phoenix).
 * Fordwin wamm, cast by Merlin to magically remove a red wine spot from Arthur's shirt (The Darkest Hour: Part One).
 * In the episode "Arthur's Bane: Part One ", Merlin appeared to have used magic to acquire a new skill, juggling. In fact, after a golden change in his eyes colour, he was able to perform in front of Queen Annis' court and amaze everyone with his abilities without revealing his magic.
 * Wearp, cast by Merlin to influence the dices he was throwing while playing with Arthur in the tavern, deciding which number was going to come out (The Diamond of the Day: Part One).
 * Gewyrc an lif, used by Emrys, right after he had regained consciousness in the Crystal Cave, to make sure his magical powers had been restored to him (they had been sucked out by a Gean Canach enchanted by Morgana). This spell created a small butterfly out of the sorcerer's hands (The Diamond of the Day: Part One).

Appearances
{| class="mw-collapsible mw-collapsed wikitable" width="100%" ! Appearances

Series 1

 * The Dragon's Call
 * The Poisoned Chalice (Presumbly)
 * The Gates of Avalon (Mentioned)
 * The Labyrinth of Gedref

Series 2

 * Beauty and the Beast
 * The Witchfinder
 * The Lady of the Lake (Mentioned)
 * Sweet Dreams

Series 3

 * Goblin's Gold
 * Gwaine
 * The Changeling
 * The Eye of the Phoenix

Series 4

 * The Darkest Hour
 * Lamia
 * The Hunter's Heart

Series 5

 * Arthur's Bane
 * The Diamond of the Day
 * }