How do you get the 2016 LMS Team Mist?
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 the 2016 esports season.”
Is the 2016 LMS Team Mist still available?
Probably not. Riot tied the 2016 LMS Team Mist to 2016 (store purchase), and it does not normally bring back past event rewards or bundles.
