From publisher blurb:
Ever adept at dark rituals, with crimson tome written in demon blood in hand, the Occultist fuses their fiendish power with common magical practices to create a refined style of spellcasting. This new Diabolic Style transforms the Fiend Binder into a proper half-caster specializing in spellcraft with efficient and effective methods that would make any lesser wizard blush. With their own specialized spell list, Occultist Fiend Binders divulge in the arcane arts to cast spells and use their empowered Fiend Shards in tandem.
Accompanying this new Diabolic Style are a set of new arcane implements: unique Fiend Shards to bolster oneself and summon dark minions, spells that weaponize false blades and conjure the energies of Hell, and special magical artifacts that grant a more expanded use of the dark essence Fiend Binders use so readily.
With this supplement, you can find the following:
One Diabolic Style: the Occultist.
Eighteen Fiend Shards spanning all available levels.
One Crystalized Focus for the Occultist.
Eight spells of 1st to 5th level.
Eight essence-based magic items.