Scourge of Duriel is a Unique Flail in Diablo IV Season 15. It comes from Duriel (Lair Boss loot table); Duriel (Lair Boss loot table, boosted class-unique drop).
Unique power
Umbral Chains gains the Epicenter Variant for free and deals [60 - 80]%[x] increased damage.
Affixes
Weapon Damage
Skill Ranks to Umbral Chains
Where it drops
Duriel (Lair Boss loot table)
Duriel (Lair Boss loot table, boosted class-unique drop)