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 (1d8) piercing damage. If the target is a creature, it must succeed on a DC 10 Strength saving throw or be knocked prone.
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:
At will: detect evil and good, druidcraft, pass without trace
Magic Resistance. The unicorn has advantage on saving throws against spells and other magical effects.
Magic Weapons. The unicorn's weapon attacks are magical.
Horn. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage.
Healing Touch (1/Day). The unicorn touches another creature with its horn. The target magically regains 11 (2d8 + 2) hit points. In addition, the touch removes all diseases and neutralizes all poisons afflicting the target.
The unicorn can take 3 legendary actions, choosing from the options below. Only one legendary action option 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.
Shimmering Shield (Costs 2 Actions). The unicorn creates a shimmering, magical field around itself or another creature it can see within 60 feet 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.