Shapechanger. The elder 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 is transformed. It reverts to its true form if it dies.

Adhesive (Object Form Only). The elder mimic can choose to adhere to anything that touches it. A Huge or smaller creature adhered to the elder mimic is also grappled by it (escape DC 20). Ability checks made to escape this grapple have disadvantage, and teleportation and planar travel to escape this grapple requires the caster to succeed on a DC 20 Charisma saving throw.

False Appearance (Object Form Only). While the elder mimic remains motionless, it is indistinguishable from an ordinary object. Magic and class features used to discern creature type does not reveal the elder mimic as a creature.

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

Innate Spellcasting. The elder mimic's innate spellcasting ability is Intelligence (spell save DC 22). It can innately cast the following spells, requiring no components:

At will: plane shift (self only)

3/day each: dimension door, charm person (9th level)

1/day each: plane shift

Pseudopod. Melee Weapon Attack: +16 to hit, reach 25 ft., one target. Hit: 28 (4d8 + 10) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite. Melee Weapon Attack: +16 to hit, reach 5 ft., one target. Hit: 50 (16d4 + 10) piercing damage plus 10 (1d20) acid damage. This attack action cannot target a creature that is not currently being grappled by the elder mimic.

Swallow. When a creature grappled by the elder mimic dies, the elder mimic can use its reaction to swallow the creature, destroying the body, healing the elder mimic for half of the swallowed creature''s maximum hit points.