|Out of universe information|
Torri Higginson- (in Elizabeth Weir's body).
She fought against Thalan until they were the last two fighters to the extent that she was able to learn his strengths and weaknesses. When her ship was damaged, she was forced to eject and she survived in a stasis pod in the Kohal system long into old age.
Her pod was retrieved by Lt. Colonel John Sheppard's team in a Puddle Jumper and taken to Atlantis. Her consciousness, stored in the headrest of the pod, downloaded itself into Dr. Elizabeth Weir (who happened to be in close proximity).
Phoebus awoke in the Atlantis infirmary. Pretending to be benign, she told the Atlantis staff that she had a limited amount of time before her consciousness was erased from Weir, and that the other pod held her husband, Thalan. To drive her lie home, Phoebus faked Weir's personality (using her memories) and managed to convince Sheppard to allow Thalan, who was as old as she, to migrate into his body so that she could properly say goodbye.
Sheppard agreed, but unfortunately, once Thalan had gained control, it was obvious that the two were the coldest of enemies. Phoebus and Thalan, now in Weir and Sheppard, went on a rampage through Atlantis in an attempt to annihilate each other for the vindication of their respective races.
When she had Sheppard/Thalan cornered, Phoebus used Weir's access codes to threaten to vent Halon gas into the Atlantis living quarters if Teyla Emmagan did not kill Sheppard, whom Phoebus could see via a monitor. Dr. Rodney McKay was able to lock Phoebus out of the system in time before she could do any damage, preventing Teyla from sacrificing Sheppard.
It may have been Thalan who had the honor of disabling Phoebus. When Weir/Phoebus had Teyla and Sheppard/Thalan cornered, Teyla armed Thalan with a Wraith handblaster, knowing he would fire upon Weir either way, which he used to take her down.
Having been in a war against her sworn enemy, Thalan for most of her life, Phoebus's desire to kill him has developed into an obsession to the point where she is willing to do whatever it takes to kill him. She is also ruthless and has no concern for the lives of Atlantis' residents which is shown when she announces of her intention to release halon gas into Atlantis living quarters if Thalan/Sheppard is not brought to her, implying that she might have a psychotic or sociopathic nature. In addition to that and just like Thalan, Phoebus is also skilled in hand-to-hand combat and heavy weaponry. (ATL: "The Long Goodbye")