Filch Lizard

From Rebirth of the Night Wiki

Filch Lizards are small passive creatures that reside within Overworld deserts. While they do not attack the player, they will occasionally steal a valuable item from the player's inventory, including rare materials, tools and weapons, and more. Upon doing so, they will scurry away very quickly.

In order to recover this item, the player must bonk the lizard (killing it is a great option but not the only way to get your items back). While holding an item, the lizard will not despawn, although it may die from natural causes and lose the item anyways.