Aglinde
The maiden daughter of King Nascor.
The devil tricked her brother, Nabor, into raping her by a spring, but Aglinda prayed, and Nabor fell dead.
In memory of Aglinda’s plight, the spring was called the Spring of the Virgin, and it was enchanted to paralyze visiting non-virgin knights. Erec became one of its victims.
Source
Post-Vulgate Queste del Saint Graal | 1230-1240