How do you get the Dragon Trainer Heimerdinger Icon?
It was a mission or event reward. Riot's description in the client reads: “Earned by purchasing the Dragon Trainer Heimerdinger bundle in the store in 2018.”
Is the Dragon Trainer Heimerdinger Icon still available?
No. Riot lists the Dragon Trainer Heimerdinger Icon as a legacy icon. Legacy icons are out of regular rotation and return only during occasional events or promotions.
