Confidence:StrongSolidPlausibleTentativeSpeculative

• Mirror Room // Fractured Realm

  2U5UU

  Enchantment — Room // Enchantment — RoomU

  Mirror Room makes Herald's Horn's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.
• Echoes of Eternity

  3CCC

  Kindred Enchantment — EldraziC

  Echoes of Eternity makes Herald's Horn's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.