One thing has always puzzled me in SU. When they fight the Gem monsters, they say they are corrupted. What corrupts them? We have seen at least with the Centipeetle that it used to look like the Gems we've seen so far. (Garnet, Amethyst, Pearl, Lapis, Peridot, Jasper, Rose)
So seriously, what the heck corrupts them and how?