Known as Arthur Pendragon, but Pendragon is not a surname but a title meaning something like "head of warriors" in Welsh, which could translate as "warlord" or "chieftain". Arthur was not a king, but a warlord in the service of a king, possibly Maelgwn Gwynedd, king of Gywnedd and one of the most powerful British lords of the time. If we seek a comparable figure we have a very close resemblance: El Cid, although we could say that he himself was king (from Valencia).
Like another famous fantastic magician Merlin was also known by many names, such as Emrys, Llallogan or Ambrosius, but his original name was Welsh: Myrddin, later latinized as Merlin. The first reference to Merlin is found in Armes Prydein, Y Gododdin, and his role of prophet or counselor was drifting towards its designation as magician.His biography varies widely according to sources, but it's remarkable his relation with the kingdom of Dyfed (it is said that he was the illegitimate son of a princess), their advice on Vortigern when building Dinas Emrys and its role as guardian of the young Arthur, along with Cynyr Ceinfarfog. Later he directed his steps towards the north after the battle of Camlann, heading to the court of King Gwendoleu. He remained there until his new employer went to war against the kings of Strathclyde and Ebrauc. After the death of Gwndoleu in Battle of Ardderyd it is said that Merlin went mad and disappeared into the wilderness.