This idea was from a friend of mine, we were working on a Sea of Thieves fanfic and think up things and creatures to add to story to flash out our story. The idea was good, I thought it would be cool if we had that enemy in-game.
The Chest Hermit Crab or better known as the Loot Crab is a species of giant Hermit Crabs that have grown to unless size.
https://www.artstation.com/artwork/o2BNRq
https://jacobkeen.artstation.com/projects/L2JxY0
https://www.artstation.com/artwork/v12Gm3
To quote my Friend: "These crabs have made their homes out of forgotten treasure chests and are well aware of the greed pirates have for their new found homes. So, in acting in spirit of being a cross between a Mimic and a Loot Rat, the second it is grabbed by an unlucky pirate. The creature will strike out defensively before instantly trying to quickly scuttle away to either rebury itself or to just simply escape the pirates that are chasing it. However, these pesky critters have one weakness and that is fire, set one ablaze and it will be cooked alive as it roasts in its chest home. Which also makes it quite the meal for those who can catch it."