A powerful Wizard and most valuable that formed the Society altogether.
Merlin is a wizard, and is widely considered to be the most powerful in the world. He is a very wise character who believes in the philosophy of "Brain over Brawn". Merlin is shown to have a wide variety of abilities including the ability to see into the future, the ability to enchant various objects and people, and the ability to travel through time, among other powers. Despite his power, he can be absentminded and forgetful.
Merlin ends up in Traverse Town. He lives in a ramshackled house hidden in a secret underground lake behind a wooden door with a fire symbol, located in the Third District of Traverse Town. He lives with the Fairy Godmother. Sora, Donald and Goofy first meet Merlin when they are supposed to deliver an old book to him. Merlin appears in a puff of smoke to greet them. Merlin teaches Sora and his friends how to properly use magic. The upper level of his house is empty and can be used for magical training against enchanted furniture.
Merlin now lives in Hollow Bastion which is being rebuilt. He lives in a large cottage which serves as the headquarters for the Hollow Bastion Restoration Committee. Merlin is part of the committee along with Leon, Yuffie, Aerith, and Cid. Upon reuniting with Sora, he grants Sora the Blizzard element. Merlin gives Sora his first Summon charm which unlocks Chicken Little. Merlin also retrieves the 100 Acre Wood book from Traverse Town's Zero District and places it on a shelf in his house. Later, he travels to Disney Castle with Sora, Donald, and Goofy to open up a magical door to the past. Merlin seems to have developed a rivalry with Cid, who prefers technology to magic, while Merlin prefers magic to technology. Their rivalry nearly gets out of hand when Cid calls Merlin an "old loon", and Merlin zaps Hollow Bastion's power computer, but thanks to Sora, Donald and Goofy, the town's systems are saved. Merlin and Cid later recall that Hollow Bastion was formerly called Radiant Garden and decide to rename it to its former name.
Merlin took an important role as their mentor, consultant and even powerful wizards there is. he also helping building the Safe house and few of the pocket dimension to help the refugee to take shelter( although, it wasn't he hoping to expect to turn good anyway.)