Mimic House

Actions

Pseudopod. Melee Weapon Attack: +8 to hit, reach 15 ft., one target. Hit: 27 4d10+5 bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.   Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 27 4d10+5 piercing damage plus 22 4d10 acid damage. If the target is a Medium or smaller creature, it must succeed on a DC 16 Dexterity saving throw or be swallowed by the mimic. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the mimic, and it takes 10 (3d6) acid damage at the start of each of the mimic's turns.   If the mimic takes 15 damage or more on a single turn from a creature inside it, the mimic must succeed on a DC 21 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the mimic. If the mimic dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.

Lair Actions

Acid Spray. The house begins leaking acid from the gaps in the boards. Anyone inside must make a DC 17 Dexterity saving throw or take 3d6 acid damage, halved on a success.   Digest. The mimic deals an additional 1d6 acid damage to any creatures it has swallowed currently. If a creature is reduced to 0 hit points this way, their body dissolves as a result of the corrosion.   Prepare. If a creature is currently swallowed, the mimic has advantage on a Constitution saving throw to regurgitate until this time next turn.

The lair is the house. Basically Monster House.