Here is another installment of exTRAPaganza, our Thursday over-the-top trap series.
These caves smell slightly of Sulphur. As the party descends into the cave, it slowly gets hotter. After the first hour, each person in the cave must make an average Constitution saving throw. On a failure, the target gains one level of exhaustion. Each hour, the save must be made again, getting progressively harder, adding 1 or 2 to the DC each time.