From publisher blurb:
Bargaining with devils and sapping the strength of demons, the artful Fiend Binder harnesses the power they gain through meddling with evil forces by channeling it through dark crystals. The Fiend Binder is a class that pulls from the abilities of fiendish entities, condensing them into crystalline shards and using them for their gain at little cost to themselves. They are the foremost experts on fiends, strange and rambunctious as they might seem, treading dark waters that would drive anyone else mad.
No two Fiend Binders are truly the same, as fiendish power can manifest in many different ways; through the thirty Fiend Shards to choose from within this book; particular tools of the trade in Crystalized Foci, special magic items crafted specifically for Fiend Binders; and the Diabolic Styles they employ to suit their needs and personalities, and to cope with the gnawing presence in the backs of their minds. The six Diabolic Styles contained within all feature different themes and playstyles, from stylish martial fighters to pact-making spellcasters. These subclasses include:
Amalgam. Beings infused with otherworldly power that allows them to undergo one of four fiendish transformations to utilize the strength of devils and demons.
Belligerent. Impressive melee combatants with supreme focus and a highly customizable fighting style that can use powerful abilities the better they perform in combat.
Dark Slayer. Fiendish fighters that employ a swift and brutal fighting style that releases pure infernal energy upon those unlucky enough to meet their blades.
Faustian. Warlock-esque spellcasters that make pacts with archfiends to empower their devilish spellcasting, reaping all of the benefits of a pact, but almost none of the cost.
Trickster. Ghostlike masters of battlefield mobility, dodging and weaving around enemy and ally like a shadow cast by a bright sun.
Triggerman. Masters of war who win the battle with a single pull of their infernal firearm’s trigger and the hellish blast of gunpowder and shrapnel it releases.