In numerous areas of Raven's Bane, you are required to kill all scarecrows in order to advance to the next area or to advance quest objectives. The Blue ray from Prismatic Spray/Prismatic Ray makes the quest impossible to complete. The scarecrow is no longer "active" and cannot be damaged by spells or melee damage. The duration of the Blue ray is permanent.
Also, ran into yet another quest objective advancement bug. Don't know how to repeat this one, but we managed to get into the hut, drive off Baba and loot the end chest yet the quest advancement was stuck on entering the hut.