Merlin

Merlin (Merlyn, Myrddin, Merlinus) is a supposed mythical figure that was the guide and help for King Arthur.

Vala stole a tablet written in Ancient code. The tablet told of an incredible treasure hidden on Earth and the man who carved the tablet was named Myrddin. This Myrddin was found in the list of names of the Ancients who returned from Atlantis to Earth more than 10 000 years ago to get away from the Wraith. Myrddin, Daniel Jackson discovers, is a name variant of Merlin from the legend of King Arthur.

They localised where the treasure might be located, at the Tor of Glastonbury and the Isle of Avalon. With help of the Asgard sensors on the USS Prometheus and the Ring transporter, Cameron Mitchell, Daniel, Teal'c and Vala came into a large cavern and were shortly thereafter faced with a sword in a stone and a holographic image of Merlin. The hologram gave his message, addressed to the Knights of the Round Table, telling them that they would have to prove they had truth of spirit and wealth of knowledge in order to obtain the treasures hidden in the underworld, the storehouse of riches of Ambrosius Aurelianus, the name attributed to King Arthur in some versions of Arthurian legend.

Possibly was Merlin an Ancient who was at an advanced evolutionary stage, but not yet ascended and he could have helped King Arthur to ascend. (SG1: "Avalon, Part 1")