Innate Spellcasting. The unicorn's innate spellcasting ability is Charisma (spell save DC 14). The unicorn can innately cast the following spells, requiring no components:
Charge. If the unicorn moves at least 20 ft. 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.
Magic Resistance. The unicorn has advantage on saving throws against spells and other magical effects.
Magic Weapons. The unicorn's weapon attacks are magical.
The unicorn can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The unicorn regains spent legendary actions at the start of its turn.
Hooves. The unicorn makes one attack with its hooves.
Shimmering Shield (Costs 2 Actions). The unicorn creates a shimmering, magical field around itself or another creature it can see within 60 ft. of it. The target gains a +2 bonus to AC until the end of the unicorn's next turn.
Heal Self (Costs 3 Actions). The unicorn magically regains 11 2d8+2 hit points.