Minicargo are covered in a constant crust of cooled basalt, slowing their movements but making them resistant to physical harm. Their movement is accompanied by loud cracking noises, their skin of basalt breaking apart and re-sealing as they move.
The shell on its back is made of hardened magma. Originally making its home in the ozone layer, it hurtles to the ground when the shell enclosing its body grows too heavy.
