Pit of Hunger (5e Trap)
From D&D Wiki
Pit Of Hunger
A simple trap door with a DC 15 Perception or Investigation check to find the trap.
When stepped on it requires a DC 15 DEX save in order to escape if fails the character falls down 20ft taking 2d6 bludgeoning damage.
The pit can be climbed out with a DC 17 Athletics. After 30 seconds the ground starts to grow teeth and begin to flip on into itself. Players take 1d6+1d8 piercing damage each round while on the floor and must make DC 10 DEX saving throw to not fall into the "belly".
When a Player falls into the belly they take 3d8 acid damage per round for 5 rounds after that the trap spits them back out to where they fell in and spends 5 minutes rearming itself.