Clockwork Unicorn

Charge. If the unicorn moves at least 20 feet straight toward a target and then hits it with a horn attack on the same turn, the target takes an extra 9 (2d8) piercing damage. If the target is a creature, it must succeed on a DC 15 Strength saving throw or be knocked prone.

Antimagic Susceptibility. The unicorn is incapacitated while in the area of an antimagic field. If targeted by dispel magic, the unicorn must succeed on a Constitution saving throw against the caster's spell save DC or fall unconscious for 1 minute.

Constructed Nature. A clockwork unicorn doesn't require air, food, drink, or sleep. It is also immune to spell saving throws against being charmed or frightened.

Multiattack. The unicorn makes two attacks: one with its hooves and one with its horn.

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

Horn. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage.