Hourglass Room

Fine sand covers the floor of this circular chamber. The only way forward is through a door on the far side of the room.

Both the room’s entrance and the far door are positioned just above the surface of the sand. A creature that steps into the room sinks waist deep into the fine particles (Small characters sink chest deep instead). The sand is difficult terrain for creatures moving through it.

A magic sensor above the opposite door activates if a living creature enters the room, causing a trap door in the center of the room to open. Sand begins pouring through the trap door. Roll initiative.

• Round One: A creature that starts its turn in the sand must make a Strength saving throw or be pulled 10 feet toward the center of the room. A creature that enters the trapdoor’s space is pulled beneath the sand and sucked through the trap door. The creature falls 30 feet into an identically shaped room below the upper chamber, taking 10 (3d6) bludgeoning damage and landing prone .
• Round Two: The level of sand in the upper chamber lowers; creatures standing in the chamber are now 10 feet below the doors and must make an Athletics check to reach either door.
• Round Four: The sand empties entirely from the upper chamber. The floor there is no longer difficult terrain .
• Round Five: At the start of round five, the two chambers rotate, so that the upper chamber becomes the lower chamber and vice versa. A creature in either area when the chambers rotate make a Dexterity saving throw . On a failed save, the creature takes 21 (6d6) bludgeoning damage and falls prone . On a success, the creature takes half damage and doesn’t fall prone.

The trap repeats until disabled or once all living creatures leave the room. Creatures capable of flying can navigate the area safely, even when the chambers rotate.

Walls. A Perception check or an examination of the room reveals that the walls of the chamber slope slightly toward the center of the area, like the sides of an hourglass.

Doors. Opening the door on the far side of the upper chamber reveals a blank stone wall. An identical door in the lower chamber opens into a control room containing the enormous gear that turns the chambers, a set of stairs that return to the landing outside the upper chamber’s entrance, and a passageway that leads deeper into the dungeon.

Landing. A creature that searches the landing outside the chamber’s entrance can make an Investigation check to discover a secret door. A set of steps beyond the door descends to the control room. The stairs allow creatures to bypass the hourglass chambers.

Sensors. A detect magic spell reveals an aura of divination magic from the sensor. There is an identical sensor in the lower chamber. Casting dispel magic on a magical sensor deactivates it, preventing that sensor from detecting living creatures in the area.

Trap Door. A creature able to access the trap door while it is clear of sand can jam it shut with a thieves’ tools check. This prevents the sand from moving between the two chambers but doesn’t stop the chambers from rotating.