What happens when a mimic gets dumped into a bag of holding? Well, it stops pretending to be whatever it was and starts to chew its way out. Not all of them, of course. Most go into stasis and those that awake often suffocate. But every once in a while, one digests the magic holding it. Thus, a knapping mimic is born. While it is limited to one magical form, it finds itself dragged all across the world with creatures that love to cause carnage. Carnage it can feast on. If worse comes to worse, well, adventurers are easy to eat when they are asleep.

Knapping Mimic

Medium Monstrosity (shapechanger), neutral

Armor Class 11 (natural armor)

76 (9d8 + 36)

Speed 20 ft

Climb 10 ft

Str 15 Dex 10 Con 18 Int 5 Wis 15 Cha 8

Skills Stealth +4, Survival +4

Damage Resistances cold

Damage Immunities acid

Condition Immunities prone

Sensesdarkvision 60 ft, passive Perception 12

Languages -

Challenge 3 (700 XP)

Shapechanger.

The mimic can use its action to polymorph into a magical backpack 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 Large or smaller creature adhered to the mimic is also grappled by it (escape DC 12). 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 magical backpack.

Grappler.

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

Gullet (Object Form Only).

The mimic's backpack interior can hold up to 8 cubic feet or 80 pounds of material. The mimic always weighs 5 pounds regardless of its contents. Storing or retrieving an object from the mimic takes an action from the creature reaching into it, or the mimic's Cough Up reaction. If the mimic dies or shapechanges to its natural form, all contents stored within it drop into its square. If the mimic swallows a bag of holding, portable hole, or similar item while in this form, it automatically dies.

Roughing It (Object Form Only).

A creature attuned to the mimic and wearing it in object form gains resistance from cold, the Survival skill if they do not have it, and advantage on Strength (Athletics) checks when climbing if the mimic is not incapacitated.

Spider Climb.

The mimic can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Actions

Pseudopod.

Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite.

Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) piercing damage plus 4 (1d8) acid damage. A creature must succeed on a DC 12 Strength save or the mimic swallows an object it is brandishing if it is medium size or smaller which is then subject to the Gullet ability.

Reactions

Cough Up (Object Form Only).

The mimic gives an object to the creature reaching into it.