Vengeful Sinew is a Unique Chest Armor in Diablo IV Season 15. It comes from The Butcher (Lord of Hatred Lair Boss) per one guide; Random world drop / any Lair Boss (one guide: 'drops at any Difficulty Tier, increased drop rate per Torment tier'); 3.2.1: all Uniques drop from level 1 in any Difficulty; targetable via Horadric Cube reroll.
Unique power
Bone Spirit explodes an additional time, dealing [35 - 45]% of normal damage. Bone Spirit deals [30 - 40]%[x] increased damage.
Affixes
+1-3 to Bone Spirit
Where it drops
The Butcher (Lord of Hatred Lair Boss) per one guide
Random world drop / any Lair Boss (one guide: 'drops at any Difficulty Tier, increased drop rate per Torment tier'); 3.2.1: all Uniques drop from level 1 in any Difficulty; targetable via Horadric Cube reroll