*** Difficulty does NOT effect this Achievement***
If you find yourself struggling at all in this game, you can pause and change difficulty from the default "normal" to "story"to make it easier.
This achievement is unlocked by completing the "Forest Road" level.
Goal: Kill Chamberlain Boss. I killed the other enemies first, then focused on Chamberlain. He has multiple spells which can confuse one of your team members so they run around out of your control for a turn or 2, or worse can actually turn one of your team against you. Do your best to focus damage on on him and only heal if you need to.
Try to always have a type of Fighter, Scout, and Mender in your group.