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 - Enemies hit by your abilities have 40% reduced healing for 5 seconds.
PASSIVE - This item grants 2 MP5 per 10% of your missing Mana. Your damaging abilities deal an extra 15 true damage to minions. Can be upgraded at level 20.