Hellhammer is a Unique Two-Handed Mace in Diablo IV Season 15. It drops from Andariel (Echo of Andariel).
Unique power
Upheaval gains the Iron Burst Variant and deals [60.0 - 75.0]%[x] increased damage.
Affixes
Weapon Damage
+Ranks to Upheaval (1 - 3)
Where it drops
Andariel (Lair Boss hoard - targeted drop)
Any Lair Boss general unique pool / world drop at Torment (chance rises per Torment tier)
Horadric Cube: Item Transmutation - Upgrade to Unique (Common base of same type + 1 Enhanced Primordial Dust + 10 Primordial Dust) rolls a random unique of that item category