Gu world is the world setting of a Chinese web novel, Reverend Insanity. Extremely harsh world of unique cultivation system that uses insects with unique ability as power. Gu masters can ascend to Gu immortals, and they obtain a virtual space inside them. Heaven hates immortals so it will generate tribulation to destroy virtual space. Each ascension of Gu immortal or to raise rank of Gu immortal will also incur tribulation. Refinement of gu and progressing through rank is exponentially hard.