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.

Special Equipment.  The mimic carries a wand of web, which also functions as a club.

Adhesive (Object Form Only). The mimic adheres to anything that touches it. A Huge or smaller creature adhered to the mimic is also grappled by it (escape DC 16). 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.

Magic Resistance. The mimic has advantage on saving throws against spells and other magical effects

Spellcasting. The mimic is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). The mimic can cast shield and misty step at will and has the following wizard spells prepared:

Cantrips (at will): acid splash, chill touch, prestidigitation, ray of frost, shocking grasp

1st level (4 slots): absorb elements, charm person, mage armor, grease

2nd level (3 slots): acid arrow, scorching ray, see invisibility

3rd level (3 slots): counterspell, erupting earth, fireball

4th level (3 slots): faithful hound, fire shield, vitriolic sphere

5th level (3 slots): enervation, steel wind strike, transmute rock

6th level (1 slot): chain lightning

7th level (1 slot): finger of death

8th level (1 slot): power word stun

9th level (1 slot): psychic scream

*The mimic casts the mage armor spell on itself before combat.

Wand. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 3 (1d4 + 1) bludgeoning damage.

Pseudopod. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 5 (1d8 + 1) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 5 (1d8 + 1) piercing damage plus 4 (1d8) acid damage.