Also Known As: Court Physician
Biographical Information
Race: Human
Gender: Male
Family: Alice (ex-fiancee)
Gaius's Mother (mother) †
Affiliation: Merlin
Geoffrey of Monmouth
Arthur Pendragon
Guinevere Pendragon
Morgana Pendragon (formerly) †
Uther Pendragon
Knights of Camelot
Old Merlin (disguise)
The Knights of the Round Table
Enemies: Edwin Muirden
Morgana Pendragon
Agravaine de Bois
Alator (formerly) †
Lancelot (Shade)

Gaius is the Court Physician of Camelot and has been for the last twenty-seven to twenty-nine 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 know of his magical abilities.


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 in 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.

Before the Great Purge started and due to an unknown reason, Morgause, having inherited her mother Vivienne’s magical powers, was smuggled out of Camelot by Gaius after she was born and being brought to the high priestesses of the Old Religion. It is unknown why 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 pursued the Dragonlord, so Gaius helped Balinor to escape execution and hid him with his friend Hunith.

Gaius and Uther had been friends despite the different views on magic of which Uther had no knowledge of, since Gaius had always pretended to support the hunt on magic.

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 and Merlin

Gaius is the current guardian of Merlin, who was sent to him by his close friend, 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.

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Gaius at the Isle of the Blessed

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.

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Gaius in his chambers

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."


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 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. Gaius used his magic again to save Merlin after Morgana put the young warlock in an enchanted coma. Though he was succesful Gaius was unsure if his old heart could take the strain were he forced to use such powerful magic again.

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)