How do you get the 2016 World Championship Tier 2?
It was a mission or event reward. Riot's description in the client reads: “This icon was the second highest tier reward players could earn for participating in the Worlds 2016 in-game festivities.”
Is the 2016 World Championship Tier 2 still available?
No. Players earned the 2016 World Championship Tier 2 by reaching the second-highest reward tier of the Worlds 2016 in-game event. Riot does not rerun past events, so you cannot earn this icon anymore.
