Seeker's Armguard

The physical-defense stat that reduces incoming AD damage. Tank items, the Bastion trait, and champions or items that grant flat Armor all feed into this mechanic, alongside the handful of effects that scale a bonus off a unit's Armor value. Sunder is its inverse — a debuff that reduces enemy Armor.

The magic-defense stat that reduces incoming AP damage. Many sustain items, the Bastion frontline trait, and "Gain X Armor and Magic Resist" effects grant or scale off it; Shred is its inverse.

Scales with Ability Power (AP). Champions and effects flagged as AP-scaling get bigger damage, healing, or shield values when the holder stacks AP from items like Jeweled Gauntlet, Rabadon's Deathcap, and Nashor's Tooth, or from trait bonuses.

The carrier gains a permanent stack on each takedown (kill or assist) and keeps those stacks across rounds, unlike in-combat stacking which resets. Set 17 Ezreal is the headline example: every 8 takedowns earns him a permanent damage drone, so early-round farming compounds into late-game burst.