Sole survivor of a long-extinct civilization who were almost entirely wiped out by Phoebus's people. He fought against Phoebus until they were the last two fighters to the extent that he was able to learn her strengths and weaknesses.
Thalan survived in a stasis pod in the Kohal System long into old age, and was retrieved by John Sheppard's Puddle Jumper and taken back to Atlantis. His consciousness, stored in the pod, downloaded itself into a willing Sheppard -- who believed that that would allow Thalan to say goodbye to his wife Phoebus -- in the body of Elizabeth Weir.
Thalan played along with Phoebus's lie until the first opportunity arose to arm himself and fire on his "wife," who was in truth his mortal enemy. He pursued her in Atlantis in an attempt to annihilate her for the final vindication of his race.
After a rampage through the city Phoebus cornered Thalan, only to be shot and disabled by a Wraith stunner pistol. The last remnants of Thalan soon vanished from Sheppard's conscious mind.
The Long Goodbye - Thalan, a blood-thirsty soldier, is resurrected in the body of Colonel Sheppard, whom he uses as a pawn to kill his true target in the body of Dr. Weir.