An observation I made shortly after my first run in with Starky:
"Wait a second.... Is it just me, or does this thing look like a more childish version of the Lavos core (Lavos' true form)?"
I hold that, Lavos was one of the species that they had altered to be a supreme biological weapon, with the basic desire to achieve 'ultimate evolution.' If he had escaped from them in an unfinished state, (to be incomplete in the way of 'training' so that it may obey rather than run wild, or otherwise be uncontrollable by its creators), then it would obviously go all crazy like it did, with the whole "killing the planet" and "destroying the future" and "consuming all space and time," and all that jazz.
It's also possible, as a slight variation, that he was created from scratch, rather than mutated. The alien species would have long accepted their form as 'normal' and would have most likely created Lavos to look similar.