Shapechanger. The mimic can use its action to polymorph into a hand mirror 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 Medium or smaller creature adhered to the mimic is also grappled by it (escape DC 11). 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 mirror.

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

Innate Spellcasting. The mimic's innate spellcasting ability is Wisdom (spell save DC 11). The mimic can innately cast the following spells, requiring no material components:

1/day each: mirror image

Living Reflection. The mimic can replicate the image of anything it has seen to display as a reflection in its mirror.  The mimic communicates by displaying images, whether still or moving.

Reflective Surface. Any time the mimic is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, the mimic is unaffected, and the effect is reflected back at the caster as though it originated from the mimic, turning the caster into the target.

Pseudopod. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 3 (1d4 + 1) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 3 (1d4 + 1) piercing damage plus 2 (1d4) acid damage.