Molten Band is a Unique Ring in Diablo IV Season 15. It comes from Urivar (Lair Boss loot table).
Unique power
Your Pyromancy Critical Strike Damage is increased by 60-80% against Healthy enemies and your Pyromancy Critical Strike Chance is increased by 40-60% against Injured enemies. Killing an enemy with a Critical Strike grants both bonuses against all enemies as well as 50% Attack Speed for 4 seconds.