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 (Object Form Only). The mimic adheres to anything that touches it. A Gargantuan or smaller creature adhered to the mimic is also grappled by it (escape DC 14). Ability checks made to escape this grapple have disadvantage.

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.

Innate Spellcasting. The mimic's innate spellcasting ability is Constitution (spell save DC 14, +6 to hit with spell attacks).  The mimic can innately cast the following spells, requiring no components:

At will: create bonfire, prestidigitation, produce flame

3/day each: create food and water

1/day each:  heroes' feast

Pseudopod. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) piercing damage plus an additional 9 (2d8) fire damage.

If the target is a Small or smaller creature, it must succeed on a DC 14 Dexterity saving throw or be swallowed by the mimic. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the mimic, and it takes 7 (2d6) fire damage at the start of each of the mimic's turns.

If the mimic takes 10 damage or more on a single turn from a creature inside it, the mimic must succeed on a DC 21 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the mimic. If the mimic dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.