Aredhel

Aredhel was the wife of Karlain who was accidentally killed by her husband when a man seeking to be Karlain's apprentice attempted to rape her. An image of her appeared before Karlain in Karazhan years later due to the tower's mysterious ability to grant visions of the past and future but since Karazhan is cursed with fel magic, its visions distort the truth for malicious intent. At first, Karlain and Mardigan witnessed a false vision in which young Karlain did not have time for Aredhel and she found herself in the company of a young novice. Karlain returned home and caught her sleeping with the man. He killed them both in a rage and the vision ended. Mardigan was angered by the vision and lost himself to his beastial fury but Revil Kost placed the cloak of purity on him which warded off the tower's fel magic, allowing Mardigan to see the true vision in which Aredhel died accidentally when Karlain used a spell that vanquished her attempted rapist but accidentally also brought down debris upon her, crushing her and killing her.

Trivia

 * Aredhel's name could be a reference to Lady Aredhel Ar-Feiniel, a character in J. R. R. Tolkien's The Silmarillion.