Ghroth the Harbinger is a fictional Outer God of the Cthulhu Mythos. It was created by Ramsey Campbell for his story The Tugging. Ghroth resembles a small, rust-colored planet or moon with a single large red eye which it can close to avoid detection. It drifts throughout the universe singing its siren song, the Music of the Spheres. As it swings by a planet, any Great Old One or Outer God imprisoned or sleeping there would be awakened by its song, usually resulting in planetary scale mass extinctions of the planet's lifeforms of even the utter destruction of the entire planet. Ghroth is believed to be responsible for the periodic mass extinctions that have wiped out 90% of all life on Earth, including the extinction of the dinosaurs at the end of the Cretaceous era. It is also believed to have caused the destruction of the planet Shaggai , the home planet of the intelligent, insect-like extra-terrestrials, the Shan. For this reason Ghroth is also known by the title of Nemesis, the Death Star, after the Nemesis Theory , a theory put forward by American astronomers Raup and Sepkoski.

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• The Tugging Ramsey Campbell The Inhabitant of the Lake and Other Less-welcomed Tenants August Derleth (ed) Arkham House

• The Music Of The Spheres Kevin A. Ross Made In Goatswood Scott David Aniolowski (ed) Chaosium

• The Encyclopedia Cthulhiana Daniel Harms (ed) Chaosium