From PathfinderWiki

Viperpool is the ruined remains of Arima in Avernus, the former domain of the deceased archdevil, Typhon. When the rest of Arima was lifted into the air to become the Promised Land of Barbatos, the remainder of the dark garden-realm was cast into twilight and its ruins and serpent-dens were overtaken by the clinging vegetation of the infernal duke Furcas, who now controls Viperpool from the neighboring realm of the Hanging Marches.[1]


  1. F. Wesley Schneider and Jerome Virnich. (2015). Hell Unleashed, p. 42. Paizo Inc. ISBN 978-1-60125-757-4