Composite Pit Lord

Composite Absorption. Whenever the Pit Lord kills a creature, it may choose to absorb and copy a feature, skill, ability score, or racial trait inherent to that creature and use it as its own. The total number of traits this creature can inherit are equal to its Hit Dice. 

Innate Spellcasting. (C.A) The Pit Lord's spellcasting ability is Intelligence (spell save DC 13). The Pit Lord can innately cast the following spells, requiring no material components:

At will: darkness, detect magic, dispel magic, phantasmal force

2/day each: confusion, power word stun

1/day each: mirror image, destructive wave

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

Magic Weapons. The Pit Lords's weapon attacks are magical.

Siege Monster. The Pit Lord deals double damage to objects and structures.

Reactive (C.A). The Pit Lord can take one reaction on every turn in combat.

Charge. (C.A) If the Pit Lord moves at least 15 feet straight toward a target and then hits it with a gore attack on the same turn, the target takes an extra 22 (4d10) piercing damage. If the target is a creature, it must succeed on a DC 21 Strength saving throw or be pushed up to 20 feet away and knocked prone.

Reckless. (C.A) At the start of its turn, the Pit Lord can gain advantage on all melee weapon attack rolls it makes during that turn, but attack rolls against it have advantage until the start of its next turn.

Multiattack. (C.A) The Pit Lord makes four attacks: two with its natural weapons and two with its Halberd. Alternatively, it makes two attacks with any weapon and casts one spell.

Multiattack. The Pit Lord makes two attacks with its natural weapons or its Halberd. Alternatively, it makes one attack with any weapon and casts one spell.

Dual-bladed Halberd. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage. If the target is a Medium or smaller creature, it must make a DC 16 Dexterity save or be knocked prone.

Gore. (C.A) Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 21 (3d10 + 8) piercing damage.

Fist. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 12 (3d4 + 8) bludgeoning damage.

Fiendish Rebuke (C.A). A creature that damaged the Pit Lord, within 60ft range, is momentarily surrounded by sickly green hellish flames. The creature must make a Dexterity saving throw (DC 16), taking 1d10 fire damage and 1d10 necrotic damage on a failed save, or half as much damage on a successful one.

Benign Matter Rejection. Whenever the Pit Lord takes damage from a single attack or spell, it may choose to lose a feature, an attack, or a trait inherited by its Composite Absorption ability and halve all of the damage from that single attack. Any secondary effects or conditions applied by the attack still occur and resolve, but any ability checks and saving throws made by the Pit Lord to resist those effects are made at Disadvantage.