There existed two Gods that were formed from the same Greatworm Binding - The Sisters of Birth. They bore the concept of ‘siblings’ being formed from a parent. One governed internal gestation while the other external consisting of larvae and eggs.
When the concept of death was born both worlds began to weaken and suffer. The Sister of Larvae chose to embrace death and gradually became the God Of Decay, leaving her old home behind. Along with it, her brood of Larvae, now motherless and unguided, having grown into grotesque and ill-developed beasts.