If you completed Black Marsh Dark Brotherhood in your first session and got the keyword "Gain Ally: Shadowscale Akisha," you may have Shadowscale Akisha in play at the time when Lich Deslandra would come out. This is an issue because these two units are the backs of each other.
If quest unit: Shadowscale Akisha is in play when quest unit: Lich Deslandra would be deployed, defeat Shadowscale Akisha and split her remaining HP as bonus HP among adventurers. Then, deploy Lich Deslandra as normal.