Alright, so I've started a playthrough as with a non min/maxed Tav and I'm going to try to recreate a fresh playthrough. (I've also turned off weighted dice).
I had no problem killing commander Zhalk again, but TPK'd against the intellect devourers right after xD. If a player is just exploring blindly after rescuing Shadowheart, you can enter the chamber before the intellect devourers do. They will will start combat right next to your characters in this scenario.
