Boros Keyrune

{T}: Add {R} or {W}. {R}{W}: This artifact becomes a 1/1 red and white Soldier artifact creature with double strike until end of turn. (It deals both first-strike and regular combat damage.)

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6olpo6fslvpb1hl60j8h7c.