Thwomps are one of the non-playable characters in LEGO Dimensions 2: The Rise of Enoch, from the Super Mario franchise.
Thwomps are large stone creatures that hide on ceilings until Mario passes under them, and they will fall down in an attempt to crush him. They are usually either blue or gray in color, and may be covered in spikes. Thwomps are apparently immune to lava (despite being made of stone, which is not molten), as they will fall in on the castle levels, and then rise right back out. This makes them efficient elevators if you can get on top of them. Thwomps can be small, medium or large in size.