Bicornaclops

Charge. If the bicornaclops 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 bicornaclops innate spellcasting ability is Charisma (spell save DC 14). The bicornaclops can innately cast the following spells, requiring no components:

At will: detect evil and good, druidcraft, pass without trace

1/day each: incite greed, dispel evil and good, ensnaring strike

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

Magic Weapons. The bicornaclops weapon attacks are magical.

Multiattack. The bicornaclops 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.

Corrupting Gaze (3/Day). The bicornaclops stares down a creature it wishes ill omen on. The target creature must make a Wisdom saving throw (DC 14), or take 3d8 necrotic damage on a failure. Additionally, on a failure the creature must also make a Constitution saving throw (DC 14), or take a point of Exhaustion. 

Death Cry (1/Day).  If the bicornaclops is ever at 1/3 its maximum hit points, it can start a wailing cry to summon its abjuritive master. On a successful Charisma check (DC 15), the bicornaclops summons a Beholder next to it. Additionally, when the bicornaclops successfully summons its master, it passes away leaving only ashes and it's two horns. 

The bicornaclops 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 bicornaclops regains spent legendary actions at the start of its turn.

Hooves. The bicornaclops makes one attack with its hooves.

Fiendish Aura  (Costs 2 Actions). The bicornaclops creates a malevolent aura of fiendish nature around itself , that spands 60 feet from it. All creatures within the aura must make 2d10 necrotic damage on a failed Constitution check (DC 14). Any damage dealt to enemies, is halved and given to the bicornaclops as healing. 

Mental Charge (Costs 3 Actions). The bicornaclops focues on a single target, and pushes its mental might at them. The bicornaclops make a melee attack against the target up to a range of 30 feet away, dealing 3d8 force damage on a hit. Additionally, on a hit, the creature is pushed back 20 feet.