From publisher blurb:
In nature, maggots are immensely useful creatures which help dispose to dead tissue. Under the influence of the Evil Insect God, they can be transformed into something more – a monstrosity used to spread its power and influence over the land. To enemies of the Insect cult, these beings are called Maggot Gods. And while they carry no actual divinity within themselves, the name is not entirely unearned.
Maggot Gods are born into existence at places where Insect cults worship, usually the efforts of a intense devotion or years of sacrifice. The act corrupts an ordinary maggot and lets it grow into an unnatural hulk willing to consume live flesh. A well-prepared cult typically has several sacrificial victims ready for this purpose.
Once the Maggot God has consumed its fill, it undergoes a metamorphosis into a demigod-like being, able to travel planes by eating its way through reality. At this point, most heroes on the physical plane are only able to flee, let alone face its new form, so adventurers are encounraged to destroy all Maggot Gods before this point wherever possible.