Given the rarity and limited information on some bonus cards, this may not be a complete list of all potential bonus cards available in this Secret Lair.
Command Tower
$4.59
{T}: Add one mana of any color in your commander's color identity.
Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
