Making Avatara is much easier than creating new forms of life. Making a new form of life requires a roll against Lore: Biology and the more of a deviation it is from existing species the harder it is. Avatara, on the other hand, are sustained by the spell that created them and will die or go into suspended animation if the mana level gets too low to sustain it. Avatara can also look like almost anything, as they don't have a real metabolism. But they can't breed and they take up one of your enchantment slots permanently, so even gods don't make very many.
Decros is a demon/sage lives in Hybris. Rumors say that he's been there longer than Evander, but if you ask the few people who know, he's a relatively recent arrival. Decros lives in a small, oddly formed building that apparently has a large subterranean section which he guards furiously. He works as a sage of sorts... demanding strange and terrible prices (often pointless, metaphorical stuff like killing your sister) in return for answering questions. But it's said that he can answer almost any question... although some rumors indicate that he actually goes underground and asks whatever it is that lives below his house, instead. Decros is a very demonic-looking avatar and behaves in a highly irrational manner. He never comes out of his home unless attacked. A few people claim that he's the last of the K'al T'al, but that's probably nonsense.