Ibelis, Yblis
The daughter of the great and evil warrior Iweret.
She lived with her father in castle Dodone in the wood called Beforet. She fell in love with Lancelot after seeing him in a vision, but was distressed when she learned that Lancelot intended to combat Iweret. Despite his own love for Iblis, Lancelot engaged in the battle and won. He and Iblis were then married.
A magical mantle brought to Arthur’s court showed her to be completely true to Lancelot in both mind and body. She and Lancelot happily ruled Genewis and Dodone together and had three sons and a daughter.
See also
Chastity test | The Legend of King Arthur
Source
Lanzelet | Ulrich von Zatzikhoven, c. 1200