Ylira was a Ysandir living in the Black City. Alanna and Jonathan defeated her along with the other Ysandir when they came there. At that time Alanna was still a page while Jon was a squire. The defeat of the Ysandir made them to legends among the Bazhir, who had suffered from the Ysandir for centuries.
She only appeared in Alanna: The First Adventure.