Roll Charisma + Tactics, 1 to 5 counts a a Failure, 6 to 10 counts as a Success, total these up and apply to all rolls for the dungeon. IE if you roll a total of 2 failures and 0 success, then subtract two die from all rolls before they are made.
I'm trying to think about how to balance this out, because you have negative dice when it comes to Team Rolls basically, but auto-failing you there cuts into one of the more core things of Not Being Alone.
Trying to think of a way to handle this that'll work throughout the quest, this seemed like a good fit, but I'm not so sure right now. We'll use it and I'll maybe tip the scales on the failure/successes in some way depending on your stat and skill.