Okay, I’m sure this is a theory somewhere on here, but if it is, I haven’t seen it…
They say that Lagi was a mutated variant of a Coolia, but he transformed into a dragon, right? Dragons were a beast of the ancients if I am not mistaken, who could not reproduce. For Lagi to turn into a dragon, he had to have some form of dragonic DNA in him in some form or fashion. If dragons cannot reproduce, therefor not giving Lagi any dragon DNA, how did he suddenly begin to evolve into a dragon?