From the publisher's website:
The Mummy's Mask Player's Guide gives players all the spoiler-free information, inspiration, and new rules they'll need to create characters prepared for delving into the adventure and intrigue of the Mummy's Mask Adventure Path.
Within, players of this campaign will find everything they need to create character backgrounds tied to personalities and events vital to Pathfinder Adventure Path's exploration of some of the many ancient tombs and vast deserts of Osirion, along with new campaign—specific traits to give bold adventurers the edge they'll need to take on the strange and deadly threats faced on their quest. This player’s guide also features a view of the city of Wati where the adventure begins, as well as various class options and advice for heroes ready to explore the nation of Osirion’s many ruins.
Adventurers don't need to delve forgotten tombs unprepared! Gather your allies and let the Mummy's Mask Player's Guide start your trip into the thrill and danger of the blistering desert.