Fire Lord Ozai (TLE-104) - Avatar: The Last Airbender: Eternal-Legal

Whenever Fire Lord Ozai attacks, you may sacrifice another creature. If you do, add an amount of R equal to the sacrificed creature's power. Until end of combat, you don't lose this mana as steps end.

6: Exile the top card of each opponent's library. Until end of turn, you may play one of those cards without paying its mana cost.