Mob baggage carrier

Suggestion for a new mob: It's a magical creature found in ancient cities. It can be found rummaging through chests in the city, but without taking any items from the location. Its main use is to serve as a personal item carrier, with the same amount of space as a small chest. This mob would follow you on explorations, and you could access its interior by clicking on it. It would act as a traveling companion, carrying the items you choose to store in your backpack. It would be quite intelligent, in addition to having incredible resistance; no mob would naturally attack it, allowing it to act as a guardian of objects. I believe that adding mobs with real functions is much more interesting than adding a new item like a backpack. The player could take several of them to explore together. It would be a magical creature, so it could teleport to the player's location if they move away, just like wolves in the past. This would allow for a new traveling companion mob. Its appearance could be small, somewhat magical, with the face of some magical being, carrying a small bag on its back, and if it were to die, which should be... It would be difficult; it would drop things on the ground for the player to pick up, and that would be its function. It wouldn't attack other mobs, only carry items like a walking, faithful backpack on adventures, being found in ancient cities, emitting a faint cyan-blue glow. It would be tamed with a tag.