This is our proprietary skill rating calculation. This has nothing to do with official game ranking or MMR.
The purpose is to show player skill levels relative to other players, not estimate MMR.
PASSIVE - You gain additional Magical Power and Lifesteal scaled from missing Health. This caps at 70 power and 10% Lifesteal at 40% Health.
PASSIVE - Killing or assisting an enemy minion provides you with 1 stack, granting 1% Movement Speed and 4 Magical Power per stack. Stacks last for 10s and stack up to 4 times. Enemy gods provide 4 stacks.