Malefic Crescent is a Unique Amulet in Diablo IV Season 15. It drops from The Beast in the Ice.
Unique power
Blood Howl is automatically cast when you Shapeshift into a Werewolf and every 4 seconds while in Werewolf form. In addition, you gain [26.7-40%][x] bonus damage for 4 seconds whenever Blood Howl is triggered.
Affixes
+148 All Resist
+[1-3] to Blood Howl (1-3)
Where it drops
World drop (any difficulty, drop rate scales with Torment tier)
Dedicated drop: The Beast in the Ice (Lair Boss, Torment 1+; Boss Trophy: Distilled Fear)
Horadric Cube: Item Transmutation (Upgrade to Unique) - Common item of the same slot + 1 Enhanced Primordial Dust + 10 Primordial Dust (random Unique of that slot)
Horadric Cube: Item Transmutation (Amalgamation) - 5x Distilled Fear (Boss Trophy) rolls a Unique from this boss's pool; can roll Mythic quality with the 'Crafted' tag