Here is another installment of exTRAPaganza, our Thursday over-the-top trap series.
It appears that all of the doors in this underground complex are heavy metal sliding doors.
When ever an open door is traversed, the door shuts quickly and heavily. The target walking through the door must make an average Dexterity check or suffer 1d6 bludgeoning damage and end up on a random side of the door. The door can be easily reopened.
Targets that spend a round preparing themselves are granted advantage on the dexterity save. Distracted targets, i.e. those that are moving at more than base speed or are involved in other actions, such as combat suffer disadvantage.