How to Complete Through Another's Eyes
The objective is to bring Adelle back to her senses. To do this, Luso has to walk up to her and use the Talk command three times. Throughout the battle, Adelle will attack you, as will the other enemy units (Pit Beasts, Thunder Drake, Zaghnal). Avoid putting all of your units in the same line, because Adelle can attack in a straight line with Lennart.
After you complete the quest, you can unlock the Heritor job.