Metabot's Manual of Magical Maneuvers

Spectral Stampede

5-level Divination

A stampede of spectral wildlife charges forth in a line 30 feet long and 15 feet wide emanating from you in a direction you choose. When a creature enters the spell's area for the first time on a turn or starts its turn there, that creature must make a Dexterity saving throw. On a failed save, the creature takes 8d6 psychic damage and falls prone. On a success, it takes half as much damage and doesn't fall prone. A creature has disadvantage on the save if it was already prone.
A hostile creature treats the area of the spell as difficult terrain. Hostile creatures in the area of effect can't take reactions.