Birgi, God of Storytelling // Harnfel, Horn of Bounty

Commander is where Birgi, God of Storytelling // Harnfel, Horn of Bounty is most at home — the mana refund on each spell is at its most broken in a format built around casting many spells in sequence, and the back face gives artifact-light decks a late-game mana sink. In Pioneer and Modern, Birgi sees occasional play in Lotus Field combo and red storm variants where the mana refund strings together enough spells to either loop Lotus Field or fuel a massive Grapeshot. Legacy and Vintage have faster, more redundant storm engines and rarely need Birgi, though fringe brews do exploit the front face in similar ways. Across every format, the verdict is the same: if your deck casts multiple spells per turn and cares about mana efficiency, Birgi, God of Storytelling // Harnfel, Horn of Bounty earns its slot.