User blog comment:Slimeologist/Faux Slimentology: Plorts, and Are They Poop?/@comment-26278046-20160219045240/@comment-30434445-20161106181727

Cool! I think maybe the genetic material builds up a lot inside the largos. Then it builds up so much that it turns into a gooey, black substance. That builds up a lot in the body, so it causes some mutation and makes the slime go all black. It will rapidly consume living things to get more substances. It will try to cover the whole planet, but fortunately there is water. Water will wash away all of the black material when sprayed onto it.