Merlin the magician is one of the most colourful characters in the Arthurian Legend. Merlin is the creation of Geoffrey of Monmouth, who in his History of the Kings of Britain blended together the Welsh tale about a prophet named Myrddin with the story that the chronicler Nennius tells about Ambrosius who had no human father. Geoffrey called this character Merlinus rather than Merdinus (what would have been the Latinisation of Myrddin). Merlin is likely to be an amalgam of several well-known bards, of which Myrddin was one. The earliest mention of Myrddin is in Aneirin's The Gododdin. The other figure of this composite Merlin is probably the bard Lailoken, who is mentioned in the 12th century, Life of St. Kentigern.
In Geoffrey's book, Merlin assists Uther Pendragon and transports the stones of Stonehenge from Ireland, but there is no Arthurian connection in Geoffrey's works.
Merlin became a widely used character in the Middle Ages. Merlin is a central character in the thirteenth-century French Vulgate cycle.
Sir Thomas Malory, in the Morte d'Arthur presents Merlin as the adviser and guide to Arthur.
Tennyson makes Merlin the architect of Camelot. And Merlin features in Mark Twain. Numerous novels, poems and plays are centred around Merlin. Merlin is perhaps the most frequently portrayed Arthurian character.
Several sites associated with Merlin's birthplace, Carmarthen, the circle he constructed at Stonehenge, Merlin's Cave at Tintagel, and the wizard's well at Alderley Edge. Carmarthen, which means "Myrddin Town."
Three sites that claim to hold his grave are Marlborough, Bardsey Island, and Drumelzier.
Various stories associated with Merlin are:-
1. Vortigern died and Ambrosius became king. Merlin was his advisor. After a bloody battle with many killed, Ambrosius asked Merlin how the dead should be remembered; Merlin advised that Stonehenge be bult as a memorial. These stone needed was in in Ireland, and it needed an invasion of Ireland by Uther, who with help from Merlin brought the stones back to build Stonehenge..
2. Merlin was responsible for Arthurs conception, making Uther appear as her husband to Igraine. The result of the union was Arthur.
3. Robert de Boront repeats Geoffrey's story of Merlin's origin and embrioders it with the creation of the Round Table and the Holy Grail story. He foresees the need for a Round Table and for Arthur. He arranges the birth of Arthur as in Geoffrey. The infant Arthur is given to Merlin for safe keeping, and the King Arthur is proclaimed when the boy Arthur pulls the sword Excalibur from an anvil set on top of a stone.
4. Merlin helps Perceval fulfill the Grail Quest.
5. In Malory Merlin is the magician at the court of Camelot, fighting off the spells of Morgan Le Fay and other witches.
6. Merlin falls under the influence of the Lady of the Lake. The result being that she puts one of his own spells on him, and he is locked away in a glass tower. Tennyson shows Merlin as a tired old man who almost seems to want to be locked away.
Full references to more about Merlin at the Rochester site
Characters from King Arthur's legends