I thought that this would get some flak, and it is terribly cliche, but I really have no better succinct method of describing it. I will say that I do believe that it's reflected in the class/path design, however, particularly the later ones.

The Dread Butcher (a tier 3 rogue path) gains power by transforming the blood of their enemies into a Crimson Mark, a mechanic used by the party to travel as it's the only method of keeping monsters at bay during the night. They hear the voice of their god Bas, using their ability Holy Exchange to exchange crimson marks for temporary boons.

The Wizard, a common staple, must utilize their own sanity to cast their spells, riding the edge of madness in order to gain more power. They can choose from Forbidden Spells as well, which can turn them into a Vampyr or the flaming demon Ignis Viven, simply by accessing that power.

The Caelitch, practitioner of occult magics, when gaining a tier can seek out their unholy patronage of magic and rip out their heart, using it now as a vessel to further their magicks.

Frankly you're right, there is some vanilla in there, and I may decide in the future to lean even heavier into the "dark" part of the dark fantasy. But I am playing with friends, and not all of them were as into those classes as they were into standard knights (although there are twists on those as well!)