+4% Damage Reduction. While near an ally this bonus is doubled and** 8% of the damage they would take from champions is dealt to you instead** (cannot reduce you below 15% Health).
So if I have 
and this mastery, will my work towards the attack of my ally?
The Voids Call1 votesThis mastery actually seems very rushed and half assed... by that i mean it doesn't seem to work as it reads. So based on how it reads you'd assume you'd take 8% of any damage dealt to them by champions... except that isn't the case dots don't seem to apply to this at all.
So i'm guessing that they probably wouldn't have put the effort into coding it in a way which reflected thornmail's damage back from the secondary's portion of the damage. That said it would need to be tested to be sure.
