Shadowblood Egg

In Commander, Shadowblood Egg occupies the low end of the mana-rock spectrum — it produces no mana until you crack it, so it never accelerates your first few turns the way a Arcane Signet or Fellwar Stone does. It earns a slot only in decks where hitting a specific off-color pip on a single turn matters more than sustained acceleration. In Legacy and Vintage, it's legal but effectively invisible — formats that operate at that power level have zero interest in a one-shot, one-mana color fixer. Oathbreaker mirrors Commander's logic: if your signature spell demands a color you can't reliably produce, Shadowblood Egg is a cheap patch, but you'd almost always rather fix your mana base instead.