Who was Merlin?

Merlin is presented in a wide range of medieval literature as a prophet and wizard who lived in early medieval Britain. We do not have any strong historical evidence for Merlin’s existence, but there are many later traditions.
 

In Welsh poetry, Merlin is primarily a prophet, not a wizard. He is associated with Northern England and Southern Scotland, an area known as ‘The Old North’. According to the poems, Merlin lost his mind after the death of his lord Gwenddolau at the Battle of Arfderydd (dated in later sources to 573 AD), and then went to live out in the wild in the woods. Merlin’s sister, Gwenddydd, appears in some of the poems, and speaks with Merlin as he tells of things to come.
 

This wild Merlin is connected with another prophet, called Emrys. Emrys produces a famous prophecy that the Red Dragon of the Britons will defeat the White Dragon of the English. At least by the time of Geoffrey of Monmouth in the twelfth century, Merlin and Emrys were brought together as one figure.