How do you get the Team Builder - Mage?
It was a mission or event reward. Riot's description in the client reads: “Earned by playing 5 games as a Mage champion in Team Builder in 2014.”
Is the Team Builder - Mage still available?
No. Riot tied the Team Builder - Mage to 2014 (mission reward), and it does not normally bring back past event rewards or bundles.
