Shaggai, also known as "Chag-Hai", is a planet orbiting a binary system with green suns. It was covered by thick inhabited jungles and dark seas. It was home to insects called the Shans, as well as a mysterious being known as "The Worm that Gnaws in the Night". According to The Dweller In Darkness, it is in the depths of the cosmos, even deeper than Yuggoth. However, it could somehow be reached by beings from other worlds, as related in the Book of Eibon by Eibon himself.
The landscape of Shaggai was terrifying: black sea formed by plasma, deserts covered by glass particles, crystalline purple mountains and forests with dense vegetation.
Its current existence is in doubt due to an orbital shift, possibly caused by the collision of an asteroid (apparently the Outer God Ghroth), which brought Shaggai dangerously close to its stars. The planet began to be bombarded by massive doses of radiation. This destroyed the atmosphere, wreaking havoc on most native beings and forcing evacuation by the Shans. Millions of years passed until the appearance of new forms of life resistant to this damaging energy.