The library of Gaius is a masterpiece in many episodes. Without it, many problems wouldn't have been solved. The destiny of Camelot rests not only on the shoulders of Merlin, but also on the knowledge of Gaius, who often requires books needed from the library. The library is on a visible upstairs floor, meaning Gaius has to climb a ladder to get to it. Gaius' library is seen in almost every episode where Merlin and Gaius are in Gaius' chambers. Merlin first met Gaius when he was reaching for a book from his library, and saved his life using magic when he fell off the ladder. Arthur often refers to his library. In The Darkest Hour: Part One, when discussing how to vanquish the Dorocha, Arthur said to Gaius "somewhere in all your books, there has to be something..."
Hence, the library is the source of solving many of the problems Merlin and Camelot faces. It contains information on all kinds of locations, creatures, including creatures of magic, books, historical events, myths, legends and so on. It does not contain books on how to practice magic, and spells, as it is prohibited. The book of spells is kept separately in Merlin's room to avoid being spotted by the army of Camelot. Information that cannot be accessed through the library is accessed through The Great Dragon. An example of this is in Le Morte d'Arthur. Despite Merlin's effort to use magic to find what he needed, the books were useless at healing the fatal bite of the Questing Beast, and Merlin needed to visit the dragon, who told him of the Isle of the Blessed, where the High Priestess of the Old Religion could be confronted to strike a bargain to save Arthur's life. Whether Gaius had any books on Priestesses and the Old Religion is unknown, but he may have deliberately hidden some books from Merlin for Merlin's own safety.
Creatures of LegendEdit
Sometimes the solution of a problem lies in a book of legends. Uther never takes legends and myths seriously, but, fortunately, Gaius does.
Creatures conjured by sorceryEdit
Living creatures in CamelotEdit
It seems that the Cockatrice is not a creature of legend and lives in Camelot Kingdom.
Books of scienceEdit
Books concerned by magical objects and magical plantsEdit
Books of spellsEdit
It seems that, in Gaius' library, Gaius and Merlin found many books talking about love spells, Troll's magic, and even healing spells.
In The Wicked Day, Merlin is looking for the right spell to heal Uther until Gaius show him a book of Gwillem of Cambria. It's difficult to establish the exact boundary between a healer and a doctor, between magic and science.