Hedron

From the Super Mario Wiki

The Hedron is an obstacle in Super Paper Mario. It is encountered in the Outer Limits. The Hedron is an indestructible, rotating, blue rectangle with a yellow outline. If the player is hit by it, he takes damage. They are often encountered in groups, with quick, evasive maneuvers being required to avoid them. Flipping to 3D does not help, either; not only can Mario not move up and down, but the Hedron exists in the third dimension, as well.

[edit] Trivia

• The Hedron's name comes from a geometry suffix.