Spirit Guardians A5E

You call down spirits of divine fury, filling the area with flitting spectral forms. You choose the form taken by the spirits.

Creatures of your choice halve their Speed while in the area. When a creature enters the area for the first time on a turn or starts its turn there, it takes 3d6 radiant or necrotic damage (your choice).

The damage increases by 1d6 for each slot level above 3rd.