League of Legends Reforged Rune: Conqueror

Dealing damage to enemy champions grants stacks of Conqueror, lasting for 5 seconds, refreshing on subsequent damage against champions, and stacking up to 12 times. Gain [2 for Melee | 1 for Ranged] stacks from basic attacks and 2 stacks from abilities, spells, and item actives.

Each stack of Conqueror grants 1.08−2.4 bonus attack damage or 1.8−4 ability power, up to 12.96−28.8 bonus attack damage or 21.6−48 ability power at maximum stacks (depending on level), at which you also heal for [8% for Melee | 5% for Ranged] of the post-mitigation damage dealt against enemy champions.

Damage over time effects and ongoing sources of damage grant stacks only once every 5 seconds.