Warforged Unicorn

Charge. If the warforged 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) lightning damage. If the target is a creature, it must succeed on a DC 14 Constitution saving throw or be stunned for 1 round.

Innate Spellcasting. The warforged unicorn’s innate spellcasting ability is Intelligence (spell save DC 14). The warforged unicorn can innately cast the following spells, requiring no components:

At will: detect magic, hunter's mark, shocking grasp (2d8)

1/day each: arcane eye, call lightning, storm sphere

Lightning Absorption. Whenever the warforged unicorn is subjected to lightning damage, it takes no damage and regains a number of hit points equal to the lightning damage dealt.

Keen Sight. The warforged unicorn has advantage on Wisdom (Perception) checks that rely on sight.

Multiattack. The warforged 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: 12 (2d6 + 5) bludgeoning damage.

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

Radiant Beam (3/Day). The warforged unicorn casts a beam of white light from its horn at a target it can see;  the target must succeed a DC 14 Dexterity saving throw or be magically marked with a glowing white outline for 1 minute. While the target is glowing, the warforged unicorn and its allies have advantage on their attack rolls against it; additionally, because the glow can be seen through all non-magical barriers, the target cannot take partial cover. The effect ends prematurely if the warforged unicorn targets another creature with this attack (only one target can be marked at a time) or the warforged unicorn is incapacitated.

Startling Eyes. When a creature the warforged unicorn can see misses their attack on the warforged unicorn, it must succeed a DC 13 Charisma saving throw or its damage adjustments and condition immunities are magically relayed to the warforged unicorn. The warforged unicorn can transmit this information to allies within 50 ft. of it as a free action.