Well, the top colorless Commander staples that are also mythic rares are Mana Crypt, Mana Vault, Sword of Feast and Famine, Wurmcoil Engine, and Crucible of Worlds
The MOM versions have colored feathers on the vertical sides representing the color(s) of the card, while the Lost Caverns god cards replace the feathers with torches or pyres of some sort
In that case, it remains a colorless 6/4 Construct artifact creature with haste, and its mana value is 7
Draw a ton of cards, and then you have no hand size requirements while you do
This can be a major problem for its survivability in combat, as well as for any synergies
The full texts of these abilities are "At the beginning of the monarch's end step, that player draws a card" and "Whenever a creature deals combat damage to the monarch, its controller becomes the monarch." (2020-11-10) If the triggered ability that causes the monarch to draw a card goes on the stack and a different player becomes the monarch before that ability resolves, the first player will still draw the card