Pathfinding fails sometimes for enemies. Once happened to me Pyromancer Guardian in "the jars room" kept going up and down the ladder for few minutes (his turn ended eventually). Similar random things happened few times to other enemies too.
Another thing im notsure is a bug or im overlooking something. Attack cost for 1H mace is suppose to be 1 (according to pop up text), but during battle normal attack actually costs 2 action points (with or without shield).
