Shapechanger. The mimic can use its action to polymorph into a bag 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 Large or smaller creature adhered to the mimic is also grappled by it (escape DC 12). Ability checks made to escape this grapple have disadvantage.

Bag of Holding. The mimic functions as a normal bag of holding or handy haversack.  Placing the mimic inside an extradimensional space created by a similar item, or placing such an item in the mimic does not destroy the mimic or the item and does not open a gate to the Astral Plane.

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

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

Grab Bag. A creature the mimic has surprised or that is not aware of its nature has disadvantage on the saving throw against the mimic's Bag Grab reaction.

Pseudopod. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) piercing damage plus 3 (1d6) acid damage.

Swallow. The mimic makes one bite attack against a Medium or smaller target it is grappling. If the attack hits, the target is swallowed, and the grapple ends. The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside the mimic, and it takes 7 (2d6) acid damage at the start of each of the mimic's turns. The mimic can have only one Medium or Small creature swallowed at a time. A creature may attempt to escape by using their action to make a DC 12 Strength (Athletics) check to escape being grappled by the mimic.  If the mimic dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, exiting prone.

Bag Grab. When a Medium or smaller creature reaches reaches into the mimic to retrieve or stow an item, it must succeed on a DC 12 Dexterity saving throw.  On a failure, it is subjected to the mimic's adhesive trait.  If the saving throw fails by 5 or more, the target is swallowed by the mimic.