Hellmouth Gulf is a large bay on Cheliax's western coast on the Arcadian Ocean. It runs from Cape Kraken in the south to the Sallow Coast in the north. The islands of Thuryan and Bog Rock lie off of Hellmouth Gulf, and the village of Blackcove is the only settlement of any note. Dark sand and sharp rocks cover most of the bay's beaches, and the water often carries with it a sulfurous smell. Most travellers avoid the waters of Hellmouth Gulf, as the coastline is known for his sharp rocks that lurk just below the waterline, waiting to tear passing ships. The waters of the gulf are also home to a greatly feared sea serpent, who is usually only referred to with a sign as the local Chelish sailors are too afraid of it to speak its name. Those who must cross the region do so by a road that runs parallel to the gulf. It is believed that this coastline was created by the cataclysmic events of Earthfall in -5293 AR.
- Rob Lazzaretti. (2011). Inner Sea Poster Map Folio, p. 1. Paizo Publishing, LLC.
- Brandon Hodge. (2010). From Shore to Sea, p. 4. Paizo Publishing, LLC. ISBN 978-1-60125-257-9
- Richard Pett, Anthony Pryor, Amber E. Scott, and Ray Vallese. (2012). Mystery Monsters Revisited, p. 50. Paizo Publishing, LLC. ISBN 978-1-60125-473-3