How do you get the PROJECT: Fiora Icon?
It was sold in the League of Legends store. Riot's description in the client reads: “This icon was released in the store for purchase during 2015.”
Is the PROJECT: Fiora Icon still available?
Probably not. Riot tied the PROJECT: Fiora Icon to 2015 (store purchase), and it does not normally bring back past event rewards or bundles.
