Bonus points for having an athletic friend hold the door closed afterwards until the screaming stops.
“The screaming stops…”
“Alright, open the door.”
“… And the Infernal chanting begins.”
“Closethedoorclosethegoddamndoor.”
Idk if anyone else follows the rule of thumb of “let the party pull the same trick 3 times before you make it backfire”.
In a story, it would fail on the third try, in a game, it would never fail. I find 4th time doesn’t leave many people dissatisfied but also doesn’t let every encounter be trivialised.
Bust out your fireball empowered cultists responsibly.
I’d think of it as once to set up Chekhov’s gun, and once to use it. I think that’s a good rule, but it should be clarified in session zero.
Also, if anything depends on the environment, you don’t need rules like this and you can directly control it to make sure it doesn’t happen often enough to get boring.
I generally wait until it would have the most impact.
A couple times handling some mind-controlled guards? Yeah, sure, they’re probably pretty dumb and not going to respond well.
Keep doing it while raiding the BBEGs territory? They’re going to catch on, and it’s going to bite you in the ass. Won’t just throw out a TPK for it, but you’re going to get an in-game warning that they’re catching on, it’s just up to the players to heed it or not.
Though I will spare a party consequences if they use it again in a more clever way than before, like it becomes a step in a greater trap.
Never underestimate the power of a nice solid doorway