Carrion Mimic

Shapechanger. The mimic can use its action to polymorph into an object or back into its true, amorphous form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Adhesive  The mimic adheres to anything that touches it. A Huge or smaller creature adhered to the mimic is also grappled by it (escape DC 17). Ability checks made to escape this grapple have disadvantage. When the mimic is attacked with a melee weapon, the attacker must make a DC 13 STR check, or the weapon becomes stuck to the mimic. A weapon stuck to the mimic cannot be used to make attacks until it is freed. A creature can make a DC 13 STR check to retrieve a weapon stuck to the mimic as an action

False Appearance (Object Form Only). While the mimic remains motionless, it is indistinguishable from an ordinary object.

Grappler. The mimic has advantage on attack rolls against any creature grappled by it.

Anchored. The mimic cannot move more than 20ft from its starting position on the map

Acid Coat. Melee attacks against the mimic cause the attacker to take 1d4 acid damage. 

Multiattack: The carrion mimic makes 2 pseudopod attacks. If a creature is grappled by the mimic, the mimic can make a bite attack against one of those creatures instead. 

Pseudopod. Melee Weapon Attack: +9 to hit, reach 20 ft., one target. Hit: 14 (2d8 + 5) bludgeoning damage and 4 (1d6) acid damage. the target is then subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 16 (2d10 + 5) piercing damage plus 6 (1d10) acid damage. If the creature is grappled, it is swallowed by the mimic. For one round after being swallowed by the mimic, the creature is restrained and blinded. It cannot be damaged by creatures other than the mimic. While inside the mimic, at the start of each of it's turns, creatures inside of it take 32 (8d6) acid damage. Dealing 30 or more damage from inside the mimic forces the mimic to make a DC 25 CON save. On a failure, the creature is vomited out. After one round, the creature is moved to the mimic's stomach. They are no longer restrained and fall 50ft into a pool of acid. They take 5d6 fall damage. At the beginning of their turn, creatures within the mimic's stomach must make a DC 15 CON save or take 6d10 acid damage, or half as much on a success. If the mimic dies with creatures in its stomach, they are violently expelled 1d8x5 ft into the air, landing prone 10ft from the mimic.