Bloodletter's Curse

Unique – Vile Decay: Dealing magic damage to an enemy champion with a champion ability applies a stack of Vile Decay to them for 6 seconds, stacking up to 4 times and up to once per basic attack or ability per cast instance every 0.3 seconds. Each stack inflicts 7.5% magic resistance reduction, up to 30% at 4 stacks.

Limited to 1 Blight item.