This guy was inspired from some table top gaming my pal Gab runs.
In the world he created one of the gods seeking to destroy/corrupt is called Hastur, and he (it?) is best known for spreading madness. One of the ways he does this is by making yellow hallucinogenic mushrooms grow everywhere. People can get addicted and go mad and eventually become consumed by Hastur's taint and turn into a destructive monster known as a Bone Demon.
Hope you enjoy! One day I'll get to full color :p