Chester (5e Creature)

Small monstrosity, neutral

Armor Class 12 (natural armor)
Hit Points 22 (4d6 + 8)
Speed 30 ft.

Proficiency Bonus +2
Senses blindsight 60 ft., passive Perception 11
Languages —
Challenge 1/4 (50 XP)

Storage Monster. The space inside the chester's mouth has an interior considerably larger than the creature itself, roughly 2 feet in diameter at the mouth and 4 feet deep. This space can hold up to 500 pounds, not exceeding a volume of 64 cubic feet. The chester weighs the same regardless of the contents of this space. A friendly creature can reach in to retrieve an item from the chester as an action.
If the chester dies, all of its contents spill out into the current space.

JWatson042 on reddit

A chester is a small, usually friendly monster often confused with the common mimic. Despite the seeming similarities, they aren't evolutionarily related in the slightest.
Intelligent creatures of all creeds often seek out a chester as a familiar or traveling companion, as their supernaturally large stomachs allow them to act as a portable and convenient traveling storage container. With the DM's permission, a creature can cast the find familiar spell to summon or resurrect a deceased chester. Doing so incurs an additional consumed material component: a short length of bone with a fossilized eye attached to its end, worth at least 50 gp.