One can only speculate if this mimic is some manner of diety or not. It certainly draws energy from those worshipping it, whether it is a golden idol, winged outsider, or scaled fiend. It is also highly intelligent and plays its flock expertly, even if religion really isn't its strong suit. If it makes a misstep, the mimic merely devours the formerly devout, moves to a new area, and sets up a new following. It does the same if the blood sacrifices to it cease, or its followers refuse to take up the practice.

Idolatrous Mimic

Large monstrosity (shapechanger), neutral

Armor Class 15 (natural armor)

Hit Points 218 (19d10 + 114))

Speed 15 ft

Str 24 Dex 13 Con 22 Int 18 Wis 20 Cha 17

Saving Throws Str +15, Con +14, Wis +13

Skills Deception +11, Perception +13, Stealth +17

Damage Resistances cold, fire, poison; bludgeoning, piercing, and slashing from nonmagical attacks

Damage Immunities acid

Condition Immunities charmed, exhaustion, prone

Sensesdarkvision 60 ft, passive Perception 23

Languages All, telepathy 60 ft.

Challenge 25 (75,000 XP)

Shapechanger.

The mimic can use its action to polymorph into a celestial, fey, fiend, 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 absorbed into its mass. It reverts to its true form if it dies and any equipment it carries is spilled out in a space within 10ft of its corpse.

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 23). 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.

Immutable Form.

The mimic is immune to any spell or effect that would alter its form other than its own Shapechanger ability.

Invested.

If the mimic is currently being venerated or worshiped by any creature within 120ft, it gains advantage on all saving throws against spells and other magical effects. In addition, it regains 10 hit points at the start of each turn as long as it has at least 1 hit point.

Magic Weapons.

The mimic's weapon attacks are magical.

Actions

Multiattack.

The mimic makes a pseudopod and bite attacks. In a non-mimic form, it may always make a pseudopod attack in place of any one of the attacks that form has.

Pseudopod.

Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 9 (1d10 + 4) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite.

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 9 (1d10 + 4) piercing damage plus 4 (1d8) acid damage.

Objectification.

Target creature that the mimic can see within 120ft must succeed on a DC 21 Constitution save or be polymorphed into an object of the mimic's choice. Any equipment it is wearing or carrying isn't transformed. The creature reverts to its true form if it dies.

For the next minute, the creature repeats this save with the effect ending on success. If the creature does not succeed after this time, they are stuck in object form until either the mimic dies or uses its bonus action to end Objectification. The mimic retains this action even when polymorphed.