the ring looks like a platinum ring guard with a blood red ruby in the middle

This ring has 5+ to damage, when you equip this ring take 3d4 necrotic damage, and when you kill a creature take 4d4 necrotic damage, 

if you find multiple rings they can stack damage 2 rings +10 damage, 3 rings +15 damage so on

Notes: Damage: Melee Weapon Attacks, Damage, Combat, Jewelry