Items, NPCs, quests, objects and spells of patch 1.12.1, read live from the realm itself.

Jet Black Feather

NPC	Level	Zone	Chance
Black Slayer	46 - 48	Blasted Lands	80.9%
Bonepicker	49 - 50		80.9%
Spiteflayer Rare	52	Blasted Lands	79.0%