Replies to Justin D. Jacobson (Board Game Necromancer): Project Update: Ahem, the Hero Chooses the Wand
>1y

The base rules have some caveat that you can't "remove" the final boss. The treasure in the base that lets you spend x Spirit to remove a Level x Foe from your space - specifically disallowed for the Level 5 Boss. So I'm sure that applies here too.