He was once a world-spanning power before the Vashar greedily began to consume him. His power waned in recent ages until the third and fourth ages when he barely existed. The Vashar scoured the world seeking more pieces of his ancient flesh to farm and consume and in the fifth age, a large portion of his flesh was joined together by Illiaph Felspark. This ushered in the return of his terrible power.
The founder of flesh seeks to reunite all of his creations back into his own flesh. Ancient prophesies speak about this being consuming the gods and "making life and death into one." The meaning of this is unclear, but is likely not something the average person would consider positive. He has a particularly strong desire to consume the divine sparks of Hero Deities.
Jilin is an amorphous creature with the ability to take many forms and has the power to divide himself into multiple creatures.
Ancient texts and madmen rarely speak the name of his true form. Some say Jilin is simply one of three aspects of an even greater being.