How do you get the Pirate Poro Icon?
It was a mission or event reward. Riot's description in the client reads: “This icon was earned by gifting a friend a Bloodharbor Medallion during the 2018 Bilgewater event.”
Is the Pirate Poro Icon still available?
No. Riot tied the Pirate Poro Icon to 2018 (mission reward), and it does not normally bring back past event rewards or bundles.
