Ilyana was born and raised in a town in Daein where she was well-liked. However, she eventually decided to become a mage and left the town to seek employment. This time in her life was very difficult and she often collapsed from hunger. During one of these fainting-spells, she was found by a merchant caravan and was nursed back to health. As repayment, she decided to stay with the merchants and guard them with her magic. Prior to the events of Path of Radiance, Ilyana got separated from her group due to a Daein invasion. She was then forced into helping the Daein forces fight Ike and his friends. When she met Ike during the ensuing battle, she learned that the mercenaries were guarding her caravan friends. Upon learning this, she immediately defects from the Daein army to help Ike. Ilyana then remains with the Greil Mercenaries until the Mad King Ashnard is defeated.
A few years later in Radiant Dawn, Ilyana joins the Dawn Brigade after Sothe rescues her, Aimee, and Micaiah from a Daein prison. She then assists Micaiah in her quest to liberate Daein from Begnion's rule. After the last victory at Nevassa, Ilyana leaves Daein with the rest of the caravan. Ilyana later joins Ike's group when her merchant convoy arrives in Begnion. As the war continues, she fights in the Apostle's Army under Ike, along with the rest of the Greil Mercenaries. When Daein's army relentlessly tries to stop them, Ilyana is forced to confront her old friends from Daein on the battlefield. After the war, Ilyana continues to travel around the continent of Tellius with the merchant convoy.