how does mejai's soulstealer work?
Unique Passive - Your champion gains 8 ability power per stack, receiving 2 stacks for a kill or 1 stack for an assist. This effect can stack 20 times; you lose a third of your stacks if you die. At 20 stacks, your champion's cooldowns are reduced by 10% and 200 health and mana are restored on kills and assists.