Hot take: if you as a DM pull something like this but aren’t otherwise running a “survival” campaign with enforcement of other environment-related rules like encumberance and starvation, you’re a jerk.
You can drop lots of hints, a perception check to notice the flame of their torches has diminished and is threatening to be extinguished. They start making con saves every 2 minutes, if they fail they get dizzy, subsequent failed saves cause headaches, then vomiting. Give them heal or wisdom checks for a chance to determine what’s happening. After 3 failed checks you use the rules for holding your breath and party members with the lowest constitution begin to lose consciousness. Seems fair
Hot take: if you as a DM pull something like this but aren’t otherwise running a “survival” campaign with enforcement of other environment-related rules like encumberance and starvation, you’re a jerk.
You can drop lots of hints, a perception check to notice the flame of their torches has diminished and is threatening to be extinguished. They start making con saves every 2 minutes, if they fail they get dizzy, subsequent failed saves cause headaches, then vomiting. Give them heal or wisdom checks for a chance to determine what’s happening. After 3 failed checks you use the rules for holding your breath and party members with the lowest constitution begin to lose consciousness. Seems fair
Also, that dungeon better be pitch fuckin’ black. Torches ain’t gonna work with that shit lol