Black Mud, a Ground Type Pet Beast, is entirely covered in black soil. Due to its black body, the whites of its eyes and its teeth are exceptionally bright.
Its species' evolutionary limit is that of a High Level Pet Beast, which, in theory, should mean not many Beast Tamers would want to make a contract with it. Yet, in reality, a significant number of Beast Tamers contract with it every year.
Because it's easy to keep alive, normally satiating its hunger by eating soil.
Therefore, many Beast Tamers from less affluent families choose to make a contract with it, while a small portion of Beast Tamers are attracted by its special abilities.
Independent space and mud liquefaction.
The former means that anything swallowed by Black Mud can be stored inside its body without any damage, provided it doesn't actively absorb it, and the latter allows its body to liquefy into mud, meaning it can squeeze into any crack or crevice.
