Here is another installment of exTRAPaganza, our Thursday over-the-top trap series.
The room is a giant sphere. Several small landing, connected by ladders are on each side of the sphere. These landings are made of razor thin metal, and are very strong.
The sphere rotates 90 degrees after the party enters. Not only does this cause the party to fall, it also causes the landings which are now on the ceiling to fall.
All targets on the landings take 3d6 falling damage as they fall, along with the metal sheets. They must also make a hard Dexterity saving throw to avoid falling on the metal sheets below. On a failure, they take moderate slashing and piercing damage. Additionally, the falling sheets make an average melee attack for heavy slashing and piercing damage.