Ring of Red Furor is a Unique Ring in Diablo IV Season 15. It comes from The Butcher (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
After spending 30 Fury within 5 seconds, your next non-Channeled Core or Weapon Mastery Skill Cast within 5 seconds is a guaranteed Critical Strike and deals [50 - 60]% bonus Critical Strike Damage.
Affixes
Strength
Critical Strike Damage Multiplier (+5 - 25%)
Where it drops
The Butcher (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