Bloodsucker:

When dealing PhysicalDamage, the ring absorbs drops of enemy blood for 30 seconds, up to a maximum of 20 stacks. If the wearer takes damage equal to 30% of their HPMax within 3 seconds, the ring consumes the stored blood and heals them for 1% of their missing health, plus an additional +5% HLPower for each stack of enemy blood, lasting 10 seconds. Stacks cannot be gained while the effect lasts.