You cause the head of a creature you can see within range to reduce in size by one category -- from Medium to Small, for example. The target must make a Constitution saving throw.

On a failed save, it takes 3d6 psychic damage and the creature's Intelligence and Charisma scores are halved (rounding down). Any corresponding ability modifiers, spell save DCs, and saving throw modifiers are reduced accordingly.

If the Intelligence score drops below 3, the creature can't cast spells, activate magic items, understand language, or communicate in any intelligible way. The creature can, however, identify its friends, follow them, and even protect them.

The spell can also be ended by greater restoration, heal, or wish.