Mordred
From The Stargate Omnipedia
Illegitimate son of King Arthur, traitor to his father. Merlin, who had once known Mordred during his days on Earth, later mistook Baal for him after emerging from along sleep in an Ancient stasis unit.
KEY EPISODE
The Quest, Part 2 - After a thousand years in an Ancient stasis unit, Merlin emerges believing he is surrounded by his old friends.