*collective convergence...

"Various pods can be found floating in certain areas of this world. Noone knows how, or why they float, but they appear to be constructed from the skeletal structures of other creatures. Throughout the encasement, the creatures within will absorb the shell from the inside- and eventually emerge with their new form. Though they are always identical, the strength and properties of their bodies are determined by the parts they were able to collect for their pod. As such, it's rare to see two with the same speed or durability."