The best thing about being an ambush predator is being where the food is, or rather where the food will be. In that vein, this mimic species figured out that there are always adventurers plumbing dungeon depths and that some of the physically weakest, rogues, are always carefully probing floors for traps. So, they have become those floors. Not only do meals come to them, there is a ‘tenderizer’ close at hand as it were in the form of a spiked pit, acid bath, or the like. If hapless creatures don’t realize it is there, however, and walk over them, well all the better.

Trapdoor Mimic

Large monstrosity (shapechanger), neutral

Armor Class 10 (natural armor)

Hit Points 90 (12d10 + 24)

Speed 15ft

Climb 10ft

Str 18 Dex 8 Con 15 Int 5 Wis 14 Cha 8

Skills Stealth +3

Damage Immunities acid

Condition Immunities prone

Senses darkvision 60 ft., tremorsense 10 ft., passive Perception 1

Languages -

Challenge 3 (700 XP)

Shapechanger.

The trapdoor mimic can use its action to polymorph into a trapdoor 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 trapdoor mimic adheres to anything that touches it. A Huge or smaller creature adhered to the mimic is also grappled by it (escape DC 14). Ability checks made to escape this grapple have disadvantage.

False Appearance.

While the trap door mimic remains motionless, it is indistinguishable from an ordinary trap door.

Floor Camouflage.

As long as the trapdoor mimic remains motionless, it gains the color and texture of the floor around it. Realizing it is different than said floor requires a Wisdom (Perception) check, DC 13. If a creature sees through the Floor Camouflage, refer to the trapdoor mimic's False Appearance instead.

Grappler.

The trap door mimic

Actions

Pseudopod.

Melee Weapon Attack: +6 to hit, reach 5 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: +6 to hit, reach 5 ft., one target. Hit: 9 (2d4 + 4) piercing damage plus 4 (1d8) acid damage.

Reactions

Spit.

The trapdoor mimic may use its reaction to toss a creature it is grappling 10ft in any direction, generally into the trap the mimic is covering. The creature must then succeed on a DC 14 Dexterity save or fall prone. If the creature collides with another creature, both must succeed on a DC 14 Strength roll or fall prone.