Good evening, unless they have changed it from 8 months ago when one of my friends ran their numbers from what I gather it works like this... when the rng hit life leech the pets gets a 45 sec buff... what this buff does is all moves it uses will gain an extra 5 mana cost to their cost... bare in mind this data is 8 months old so the next value may of changed... but at that time you gained back 55-60% of the damage done as life.... I heard they might lower it to 30% but have run no test on it or heard any new data to reflect this change... Hope this helps mate.. =^-^=