Players enter the room, it locks behind them and had no handle. DC25 to pull open with strength, and you ain't gonna have time to take 20 
There is a metal pole at the center of the circular room, with a ball and chain hanging off of it made of steel. The walls and floor are extremely slick, covered in oil. There's about two inches of oil on the floor as well. Observant characters might be able to tell that the stone walls are made entirely of flint.
The pole in the center begins to spin. THe ball and chain pick up speed and eventually strike the walls, igniting the room for three rounds, doing 10d6 a round.
Other than getting the door open, characters might try breaking the chain or jamming the spinning pole.
There is a metal pole at the center of the circular room, with a ball and chain hanging off of it made of steel. The walls and floor are extremely slick, covered in oil. There's about two inches of oil on the floor as well. Observant characters might be able to tell that the stone walls are made entirely of flint.
The pole in the center begins to spin. THe ball and chain pick up speed and eventually strike the walls, igniting the room for three rounds, doing 10d6 a round.
Other than getting the door open, characters might try breaking the chain or jamming the spinning pole.
