Unbroken Chain is a Unique Amulet in Diablo IV Season 15. It comes from Urivar (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.
Unique power
Swapping weapons increases the damage of Iron Maelstrom by [25.0 - 30.0]%[x] for 5 seconds, stacking up to 3 times.
Affixes
Strength
Attack Speed (+2.0 - 10.0%)
Where it drops
Urivar (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