How do you get the Harrowing 2012 - Vengeful Wraith?
It was sold in the League of Legends store. Riot's description in the client reads: “Acquired by purchasing at least 3000 RP during the 2012 Harrowing event.”
Is the Harrowing 2012 - Vengeful Wraith still available?
Probably not. Riot tied the Harrowing 2012 - Vengeful Wraith to 2012 (store purchase), and it does not normally bring back past event rewards or bundles.
Harrowing 2012 - Vengeful Wraith is one of the rarest LoL summoner icons.
