~ Camelot ~
The information provided below is quoted from Ronan Coghlan's The Encyclopaedia of Arthurian Legends!
(in Welsh: Myrddin, latinised as Melinus becuase the more natural Merdinus would have connected it with Latin Merdus, 'dung').
Arthur's magician and counsellor, in many ways the architect of his reign. In the classic form of the tale, Merlin was begotten by an incubus. Robert says the devils of Hell had determined to set on earth an evil being to counter balance the good introduced by Jesus Christ. Happily, the child was promptly baptised, so he was not evil. Vortigern, King of Britain some time after the Roman withdrawal, was haplessly trying to build a tower for, whenever it was erected, it would collapse. The king's counsellors told him he would need to sacrifice a fatherless child to remedy this. Such children were hardly thick on the ground but Merlin, now a youth, was popularly supposed to be sireless so he was secured for this purpose. However, he pointed out that the real reason for the collapse was the existance of a pool beneath the foundations. Digging revealed the truth of this and a brace of dragons emerged, one red and one white; these caused Merlin to utter a series of Prophecies.
When Aurelius Ambrosius defeated Vortigern he wished to put up a monument. Merlin advised hime to make an expedition to Ireland to procure certain stones and these were erected on Salisbury Plain as Stonehenge.
After the death of Aurelius, when Uther came to the throne, Merlin arranged for him to seduce Igraine by magically making him take the shape of Igraine's husband, Gorlois. He took the child, born of this union, and arranged the sword-in-the-stone contest, whereby Arthur became King.
After this, according to Malory, Merlin became infatuated by Nimue (elsewhere called Vivaine), whom he taught magical secrets which she used to imprison him.
Geoffrey, however, has him active after Camlann, bringing th injured Arthur to Avalon. He then went mad after the battle of Arthuret and became a wild man, living in the woods. Accroding to Giraldus Cambrensis, this was because of sight he beheld in the sky during the fighting. He had been on the side of Rhydderch Hael, King of Cumbria, who was married to Merlin's sister, Ganieda, and three of Merlin's brothers had died in the battle. After a time, Ganieda persuaded Merlin to give up his life in the forest, but he revealed to Rydderch that she had been unfaithful to him. He decided to return to the greenwood and urged his wife Guendoleona to remarry. HOever, his madness once again took hold of hom and he turned up at the wedding, riding a stag and leading a herd of deer. in his rage, he tore the antlers from the stag and flung them at the bridegroom, killing him. He went back to the woods and Ganieda built him an observatory from which he could study the stars.
Welsh poetry antedating Geoffrey largely agrees with this account, though it has Merlin fighting against Rydderch rather than for him. Similar tales are told about a character called Lailoken, who was in Rydderch's service and this may have prompted Geoffrey to change the side which Merlin was on. As Lailoken is similar ro a Welsh word meaning 'twin brother' and as Merlin and Ganieda were thought to be twins, it is possible it was merely a nickname applied to Merlin.
Merlin is not, at any rate, a personal name but a place name - the Welsg Myrddin comes from the Celtic Maridunon(Carmarthen> - which was applied to the magician because, accoridng to Geoffrey, he came from that city. Elsewhere it is averted that the city was founded by, and named after, the wizard. Robert has him born in Brittany. Geoffrey makes him King of Powys, and the idea that he as of Royal Blood is also found in Strozzi's Venetia edificata (1624).
Merlin's mother was called Aldan in Welsh tradition, Optima in French romance and Marinaia in Pieri's Storia di Merlino(fourteenth century). The Elizabethan play The Birth of Merlin - which may have been partially authored by Shakespeare - calls her Joan Go-to-'t. That he had no father does not seem to be a feature in Wlesh tradition. He is also said to be the son of Morgan Ferych who, some claimed, had been a prince of Gwynedd.
Further snippets of informatuion found elsewhere are that he save Tristan when he was a baby; that he had a daughter called La Damosel del Grant Pui de Mont Dolerous; that he was not imprisoned by Nimue but retired voluntarily to an esplumeor or place of confinement.
Both Welsh poetry and Geoffrey have him speaking with Taliesin, with whom he seemed to be considerably connected in the Welsh mind. Thus one Welsh tradition asserted in Vortigern's time, then was reincarnated as Taliesin and reincarnated once more as Merlin the wild man.
Merlin's ghost is said to haunt Merlin's cave at Tintagel. The wizard is variously said to be buried at Drumelzier in Scotland, under Merlin's Mount in the grounds of Marlborough College, at Mynydd Fyrddin and in merlin's Hill Cave in Carmarthen.
As to the historical Merlin, if he existed at all, moden writers such as W. Rutherford and N Tolstoy think he may be a latter-day Druid and so took part in shamanistic practices.