Alicorn

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.

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, sacred flame, pass without trace, alter self (can disguise itself as a normal horse with this spell)

1/day each: calm emotions, dispel evil and good, entangle

Magic Resistance. The unicorn has advantage on saving throws against spells and other magical effects.

Magic Weapons. The unicorn's weapon attacks are magical.

Flyby. The alicorn doesn’t provoke attacks of opportunity by flying out of someone’s reach. 

Multiattack. The alicorn 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.

Healing Touch (3/Day). The alicorn 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.

Teleport (1/Day). The alicorn magically teleports itself and up to three willing creatures it can see within 5 feet of it, along with any equipment they are wearing or carrying, to a location the unicorn is familiar with, up to 1 mile away.

The alicorn 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.

Move. The alicorn moves up to half its speed.

Smite. The alicorn makes one horn attack or casts sacred flame.

Shimmering Shield (Costs 2 Actions). The alicorn 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 alicorn magically regains 11 (2d8 + 2) hit points.