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

Discolored Worg Heart

NPC	Level	Zone	Chance
Bloodsnout Worg	16 - 17	Silverpine Forest	46.4%
Mottled Worg	11 - 12	Silverpine Forest	39.2%
Worg	10 - 11	Silverpine Forest	38.9%
Gorefang Rare	13	Silverpine Forest	36.6%