Undead Unicorn

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.

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
chill touch, druidcraft, pass without trace

1/day each
false life, ray of sickness, entangle

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

Immunities
Poison.

Magic Weapons
The unicorn's weapon attacks are magical.

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.

Undead Fortitude
If damage reduces the unicorn to 0 hit points, it must make a Constitution saving throw with a DC of 5+the damage taken, unless the damage is radiant or from a critical hit. On a success, the unicorn drops to 1 hit point instead.

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

Legendary Actions
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. Spent legendary actions are regained at the start of each 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.