Nearly three-quarters of Australia remains unknown in the 1920s. It is one of the last great wildernesses and a place of secrets and discovery. Whether delving into mysteries on the streets of Sydney or mounting an expedition into the remote Outback, Australia is a fertile setting for those investigating the threats of the Cthulhu Mythos. From gang-related crimes and nefarious cults to ancient wisdom and lost cities, there is no shortage of adventure in the Land Down Under. This book provides a history of Australia, detailing both its geography and lore. Rules are presented for Australian investigators, with new skills, as well as mechanics for mounting expeditions. Law enforcement, transport, communications, and other sources provide Keepers with a toolkit of resources. Five cities are detailed. Special rules are presented for investigators to learn from the Song-Lines of the Aboriginal peoples. For Keepers, Terror Australis presents details of the Great Race, the flying polyps, and the elusive sand-dwellers, while also looking at other threats to be found lurking in Australias dark shadows. Two large scenarios showcase the mysteries and horrors awaiting the unwary: In Australia, investigator will come face-to-face with supernatural forces that have endured for aeons. It is a land of adventure, danger, and ageless wisdom-a perfect for setting for Call of Cthulhu!