How do you get the Season Year 2024 - Emerald Icon?
It was a ranked reward. Riot's description in the client reads: “This icon was earned by achieving Emerald in Season Year 2024.”
Is the Season Year 2024 - Emerald Icon still available?
No. The Season Year 2024 - Emerald Icon was a ranked reward. To earn it, you had to reach Emerald during Season 14 (2024). Riot does not hand out past ranked rewards again, so you cannot earn this icon anymore.
