Ahri Ability (LoL): Essence Theft

Whenever Ahri hits an enemy with one of her abilities, she gains a stack of Essence Theft, and can gain up to 3 stacks per ability cast.

Upon reaching 9 stacks, her next ability heals her for 3 / 5 / 9 / 18 (+9% of ability power) for each enemy hit (depending on level).