Euclidean Collapse

You impose an impossible geometric structure. Reality begins to fold inward, angles become contradictory, and distances no longer behave as they should.

Choose a point you can see within 60 feet. A 15-foot-radius cube centred on that point becomes difficult terrain. The first time a creature enters the area on a turn or starts its turn there, it must make an Intelligence saving throw or take 2d6 psychic damage. On a successful save, the creature takes half damage but still treats the area as difficult terrain.