Bacterioid

Shape Changer. Bacterioids can change their shape at will.

Spellcasting. The Bacterioid is a 4th-level spellcaster. Its spellcasting ability is 15 , with a spell save DC 18 +3 to hit with spell attacks. The Bacterioid has following spells prepared:
Cantrips (at will): Acid Splash, Infestation 
1st level (6 slots): Absorb Elements, Fog Cloud 

Sharpened Limb. Melee Weapon Attack: +20 to hit, reach 3 ft., 1 target. Hit: 82 (4d20 + 7) slashing damage. 

Flying Anvil. Ranged Weapon Attack: +20 to hit, range 50/1000 ft., 1 target. Hit: 130 (10d10 + 20) bludgeoning damage.

 Counter. After attacked, the Bacterioid can choose to duplicate the attack used on it.

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

Instantaneous Consumption (Costs 1 Action). The Bacterioid envelopes a opponent and gains health according to half of the damage they deal to the creature. They can make a DC 19 check, on a fail, they take 4d12 necrotic damage and begin to suffocate, along with being grappled. On a success, the grappling and attack fails. If creature dies, then instead of rolling the die to save themselves, they are absorbed by the Bacterioid. The Bacterioid then regains hit points equivalent to the maximum hit points of the creature it has ingested. If it would go over its natural hit point maximum, the Bacterioid gains temporary hit points equal to the remaining amount for the next day.