From publisher blurb:
The Demonologist base class is a new hybrid class by Total Party Kill Games. The Demonologist is a master of the infernal arts, a summoner of great power, who uses not eidolons, but demonic servants. He wields the dark arts like a witch, capable of maelific hexes that bind mortals and demonic ilk alike.
Within these pages lie a fantastic new class that is both fun to play and who could make a truly challenging villain unlike any other in your repertoire.
This 20 level base class comes complete with 30 new hexes, new archetypes like the Fiendflesh Disciple, the Infernal Traitor, the Sacrifist, the Rakshasa-bound Zakyas, plus 23 new feats, new spells and magic items!
Do not bow to evil, make it bow to you!