From publisher blurb:
Harness the power of an expanded suite of souls to further customize your Soulforge, or gain access to souls on other characters as an Adept Soul Forger!
Pantheon of Souls is the first major expansion to The Soulforge: Spirit of a Hero, featuring 22 new Expanded Forged Souls, options which allow a soulforge to replace some of their class's initial souls with souls themed around Pathfinder's advanced classes, akasha's classes, and a few weirder and surprising options!
Also included in this book are the optional rules for Adept Soul Forger, allowing a character to exchange some of the feats they normally gain on leveling up to gain the ability to forge a soul, and new feats to help expand the abilities of a Soulforge or Adept Soul Forger!