Sire of Sin is a Unique Ring in Diablo IV Season 15. It comes from Grigoire (Lair Boss loot table); Grigoire (Lair Boss loot table, boosted class-unique drop).
Unique power
Infernal Breath gains the Explosive Death Variant for free and deals [120 - 130]%[x] increased damage.
Affixes
Willpower
Skill Ranks to Infernal Breath
Where it drops
Grigoire (Lair Boss loot table)
Grigoire (Lair Boss loot table, boosted class-unique drop)