How do you get the Battle Queen Katarina Chroma Icon?
It was an event pass reward. Riot's description in the client reads: “This icon was acquired from the Event Pass Token Shop during the 2020 Battle Queens event.”
Is the Battle Queen Katarina Chroma Icon still available?
No. Riot tied the Battle Queen Katarina Chroma Icon to 2020 (event pass), and it does not normally bring back past event rewards or bundles.
