Multiattack

Two Hooves attacks and one Void Horn attack.

Hooves

Melee Weapon Attack: +7 to hit, 5 ft., one target, 11 (2d6+4) bludgeoning damage.

Void Horn

Melee Weapon Attack: +7 to hit, 5 ft., one target, 8 (1d8+4) force and target must make DC 13 Con save or contract the nullifying blight disease (above).

Ripple of darkness

Each creature within 20' of the nullicorn: 18 (4d8) necrotic and contracts the nullifying blight disease (above; DC 13 Con half and doesn't contract it).