Birgi, God of Storytelling // Harnfel, Horn of Bounty (J21-416) [Jumpstart: Historic Horizons]

Whenever you cast a spell, add . Until end of turn, you don't lose this mana as steps and phases end.
Creatures you control can boast twice during each of your turns rather than once.

Discard a card: Exile the top two cards of your library. You may play those cards this turn.