Action Name. 

Death Burst

When the abomination dies, it explodes in a burst of blood and bone as the demon violently leaves the body. Each creature within 10 feet of it must make a DC 15 Dex saving throw, taking 32(9d6) necrotic damage on a failed save, and half on a success.

Innate Spellcasting

The abomination's Innate spellcasting ability is Intelligence (spell Save DC 14, +5 to hit with spell attacks.) It can innately cast the following spells, requiring no material components:

At will: Charm Person, Fire Bolt, Magic Missle, Disguise Self, Minor Illusions.

2/ day Each: Burning Hands, Fear, Ray of Enfeeblement.

Absorption.

For 1 Action he gains HP (half) to the creature he absorbs and one feature from the creature absorbed (wings, weapon, jaws, Etc.)

Action Melee Attack. 

Multiattack. The abomination makes two melee attacks.

Claws. Melee Weapon Attack: +6 to hit, Reach 5ft. one target. Hit 19(5d6+4)

Necrotic Wings. 

Once per day, for 10 Mins wings of death sprout from the abomination allowing it to fly up to its walking speed. (Only if you Absorbed a creature that has wings.)

Reaction Name. Opportunity attack

Enter the description for how legendary actions work for your monster here.

Legendary Action Name (Costs # Actions). Enter the description for your legendary action.

Enter the description for how mythic actions work for your monster here.

Mythic Action Name (Costs # Actions). Enter the description for your mythic action.