So I know this is a noob question, but I rarely play this game, and so I want to know what this ability is, I think its a mastery or an item, but I don't know what it is, and how to use it, its like a blueish purple lightening strike thing
I think you refer to thunderlord which is a mastery. But its not just to finish kills, it works whenver you deal 3 tics of damage
I think it might be the Smite summoner spell augment called "Chilling Smite" which causes you to be able to smite enemy champions and it has a blue hue to it while also looking like a lightning.
It's either:
When you do 3 individual damage form's on a champion in 2 seconds, then the THUNDER DROPS!
