From the PDF introduction
One of the advantages of designing games in Washington state is the ready supply of rules-knowledgeable gamers. During the design and development of the Ghostwalk campaign, we spent a whole summer playing through two of the adventures included in the book. This weekly minicampaign allowed us to test not only the adventures but also the game rules for the setting. Playtester feedback helped shape the flavor of Manifest and its environs, and the comments we received often offered ideas and solved problems that the designers had overlooked.
Unfortunately, not everything we wanted to include would fit into the book. So without further ado, here are some additional monster templates, feats, spells, and magic items for the Ghostwalk campaign, plus an adventure seed for you to develop and the full statistics for the playtest characters. May all of these offerings enhance your players’ experiences on the other side.