Guardian

Passive: While within 350-range of an allied champion, you deem them Guarded. Allied champions you affect with unit-targeted abilities are also Guarded for 3 seconds, regardless of distance.

While an ally is Guarded, if either of you would take 70 to 240 for 15% damage within 2.5 seconds or lethal damage from an enemy champion, monster or turret, you both are shield for 45 to 180 for 15% (+ 15% of your AP) (+ 5% of your bonus health) for 2 seconds.