Merlin is a legendary personality who is well known for being the tutor of Arthur before he became a king. He has over the ages become an universal ensemble for youth seeking wisdom, material prosperity and spiritual value. Merlin is a remarkable figure in Welsh literature and Aurthurian legends. He is a man of mystery and magic, there is a lot of mystery surrounding his life. He is known for many skills – he has been mentioned as wizard or sorcerer, a bard, a prophet, an advisor and an able tutor. He was a young boy who had no father. As an old man he offered advises to four successive kings of Britain.
On the other hand he has also been mentioned as an old fool who could not control his lust on seeing beautiful women. Women hold him in fear. He went mad after a bloody battle and ran off into the forest, there he learned to talk with the wild animals and was named Wild Man of the Woods. He was thus a controversial character.
Though many scholars feel that King Aurthur, Guinevere, Merlin and Lancelot are fictional characters as their graves have still not been discovered. But many others feel that Merlin is none other than a writer and prophet named Myrrdin. Myrrdin was also a scholar of great repute in his times. Whether or not he advised the king is still not known. But he did go mad and take refuge in the forest of Celydon after King Gwenddolau was defeated in the Battle of Arderydd in 573. First mention of Merlin is seen in the History of the Kings of Britain in 1135 by Geoffrey of Monmouth. Indeed Merlin had later on become a prophet and was associated with a quest for the Holy Grail. Merlin has been mentioned to have been trapped in a hawthorn tree and he dwelled there until death. Myrddin similarly was trapped by his madness in the forest and was never seen again.
So there are strong chances that Merlin was none other than Myrddin.