Evanlyn, who's real name is Cassandra, is the Princess Royal of Araluen. King Duncan's only daughter, Cassandra created the alias Evanlyn when she was visiting the Princess of Celtica during the short war between Morgarath and Araluen. Her escort held off attacking Wargals while she escaped, and she found Ranger's Gilan, Will, and Apprentice Knight Horace. Soon after, Will and her were captured by Skandians Erak Starfollower and his Wolfship crew. After they were taken back to Skandia, the two were given as slaves to the Skandian Great Hall. Erak then helped both of them escape, while she nursed Will back to health after being addicted to warmweed.
The Battle for Skandia (The Oakleaf Bearers)
Princess Cassandra's identity was revealed by wolfship skirl Slagor, and Ragnak almost killed her. Ranger Halt proposed that the matter should be dealt with after the battle, so she was safe for that time. Cassandra also played a big part in the Battle for Skandia. She signaled Will to order the archers to fire, when she was sure they were reloaded and ready. Without her, the archers would have been ineffective, as Will said he couldn't call out the orders all at once.