From the introduction:
This is an easy conversion for all mechanics in the campaign Dead Gods from Planescape AD&D Second Edition to D&D Fifth Edition. You must own the original campaign book to use this conversion.
The original adventure was written by Monte Cook. It's designed for 4-6 characters between 6th and 9th levels, but the adventure works well for PCs of any level with very minimal modifications.
Appendix II of this document presents all text excluded from the "damaged" adventure product that circulated in some retail areas.