If you played The Fates We Weave, there's supposed to be something of a secret boss coded in. Of course, you can't really defeat him or get anything from him at this time, but I consider getting to him a challenge.
Yr'gnuh is an Old God because there was Old Gods in Bloodborne and Old Gods in Hearthstone; everyone was doing it. In this game's case, not only did he end up with an interesting animation, but I did a bit of scripting to make him stand out. Note that the eyes are the bottom of his mouth and he needs no shading.
How to unlock this boss (Current Demo) with barest hints:
1. Activate Hard Mode, Vore Mode and Random Trait Mode. While you might have a chance to get them on a new game, there is a place in the demo you can activate those options. You have to activate them before finishing the first boss.
2. Clear the Spider, Cyber Fae and Mudball Nests on Hard Mode to acquire some Wrappers.
3. Purchase Shrinky Pop.
4. Use Shrinky Pop on a hidden monster. Profit.