Once, a spelljammer wrecked on a lonely, but animal-populated asteroid. The mimic that caused the disaster found the fauna on the floating rock delicious and invigorating. It didn’t expect to mutate and grow to immense size, eventually becoming a small moon onto itself, but there it was. It wasn't long before the lunar mimic cruised the spaceways, feeding on space-born prey and dropping its spore on other verdant asteroids. Thankfully, most lunar mimics perish before they achieve their mobile stage, but even one of the horrors can devastate a stellar tradeway or wreak havoc across a planetary system.

Lunar Mimic

Gargantuan monstrosity (shapechanger), neutral

Armor Class 18 (natural armor)

Hit Points 307 (15d20 + 150)

Speed 15ft

Fly 80ft

Str 30 Dex 4 Con 30 Int 12 Wis 18 Cha 17

Saving Throws Str +16, Con +16 Damage Immunities acid, cold; bludgeoning, piercing, and slashing from nonmagical attacks

Condition Immunities prone

Sensesdarkvision 1000 ft., passive Perception 14

Languages -

Challenge 20 (25,000 XP)

Shapechanger.

The lunar mimic can use its action to polymorph into a small moon 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.

Aura of Lunacy.

The lunar mimic broadcasts a maddening psychic wave in a 100ft radius. Whenever a creature enters this area for the first time or begins their turn within it, they must succeed on a DC 18 Wisdom save or be charmed by the mimic for the next minute. While charmed by the mimic, a creature must make a melee attack before moving against a creature not charmed by the mimic of the game master's choosing. If no such creature is within reach, the creature uses its Action and Move to get closer to the mimic.

At the end of each of its turns, a charmed creature may repeat this save, the effect ending on success. Once a creature succeeds against the lunar mimic's Aura of Lunacy, it is immune to this effect for 24 hours.

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 24). Ability checks made to escape this grapple have disadvantage.

Fatal Attaction.

The lunar mimic may use its bonus action to pull a target restrained by its Focused Gravity 100ft closer to it in a straight line

False Appearance.

While the mimic remains motionless, it is indistinguishable from an ordinary small moon.

Grappler.

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

Siege Monster.

The lunar mimic deals double damage to objects and structures.

Actions

Multiattack.

The lunar mimic makes two attacks.

Pseudopod.

Melee Weapon Attack: +16 to hit, reach 50 ft., one target. Hit: 21 (2d10 + 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 15 ft., one target. Hit: 21 (2d10 + 10) piercing damage plus 9 (2d8) acid damage.

Mimicked Moonbeam (Recharge 5-6).

Ranged Spell Attack:+10 to hit, range 500/1000 ft., one target. Hit: 72 (16d8) radiant damage.

Focused Gravity (Recharge 6).

The lunar mimic chooses a target it can see within 1000ft. The target must succeed on a DC 24 Strength save or become Restrained for the next minute. The lunar mimic can only restrain 1 target at a time.