Black Marketeer of Mammon:
To collect Dark Fragments, go to the Altar of Evil. Get 50 Dark Fragments from Arbitors of Darkness, Altar of Evil Spirit Offering Boxes, Mutated Cerberuses, Dartanions, Insane Phions, Dimensional Rifters, and Hellgate Fighting Dogs.
(The Altar of Evil is in the Fog of Blood Region near the Dark Elf Village.)