As a gifted magic-user, she was trained first by the wizard Keane and later by Sinioth, an aspect of Talos. She was taught magic directly by The Storm Lord. He appeared to her as a large man, with dark brooding features.
A special ability granted to her was a powerful version of the lightning bolt spell. It appeared solid black and instantly killed anything that it hit regardless of protections or size; only greater deities were unaffected.
Deirdre was the second daughter of King Tristan and Queen Robyn Kendrick, born barely a year after her sister Alicia. As they grew up, Deirdre was often openly hostile to her sister, apparently already suffering from doubt and inadequacy that she channeled into rage. She was taught by Keane, but he stopped when he understood the void in her heart.
In the Year of the Sword, 1365 DR, Sinioth seduced her. At first, Talos used Deidre in a positive fashion, sending her to stop the Ityak-Ortheel and to save her father from sahuagin. However, afterward, Deidre became a complete pawn of Talos and the storm god used her to start a war to conquer the isles. In the end, Deidre was killed by her sister Alicia.