Slave of Darkness — Paul Wilson

A band of elves drives off the orcs slaughtering a travelling caravan in their forest. The only survivor is a baby elf girl. As she grows, Tolaine Starstrider finds herself at odds with her foster parents. Not being a pure blooded elf, she discovers a powerful force within her that she must learn to control or be consumed by. Tolaine is not the only one who knows about the strange magic she carries and she is captured by one who would use her power for his own ends.