this is on PC-EU
there is an enemy stuck somewhere under the lava that surrounds the final boss arena. if you step too close to the edge (usually the right edge) after defeating the Lava Queen, you may accidentally enter into combat with that enemy. since you can't really tell for sure where the enemy is you're only option is to blindly throw AoEs and even that is difficult so you are bound to remain stuck in combat. this means you can't enter the exit route and you'll miss out on any remaining story content or loot