What worries me now is that we can't teleport everyone out to safety. As long as we had that I wasn't too worried. Now two will die here if if all goes badly. I feel that either the two newcomers sneak out now and get to their flying mounts and prepare to leave or we all just commit to fight to the end. One person needs to teleport the mask out regardless though.
It's a tough spot when the maguffin is found near the beginning of the dungeon, but you still want to do the dungeon because you are here to play Dungeons & Dragons. Pushing it further can be justified in character, or for out of character reasons (I.e. For fun).
Ah, but are you doing the dungeon because you need to, or are you getting greedy because of the valuables temptingly laid out before you? A dragons hoard, a flying castle both are fabulous wealth and magic. But your healers have no spells left, your wizards are down to low level slots, and half your tanks are double exhausted. Is the reward iworth that kind of risk? Also, we now have a map to all the cultists strongholds, giving us a lot of adventuring ahead to clear them out.