Ruby/Amethyst and Emerald/Steel are both great color combos, so these may well be easy to upgrade
"The idea here being that this card represents the D&D Beyond team becoming WotC employees", Mooney says
It taught me how trample actually worked, gave me my first taste of playing with the power nine, and stole hundreds of hours of time
You could also go artifacts or enchantments, since there are also many artifact creatures and enchantment creatures, especially ones that would give you additional cost reduction
Then, at the start of your end step, you get to bring back a creature from your graveyard back to the battlefield, so long as its power is less than Mirkos
It was so bad, in fact, that Wizards utilized bans to try and spice things up for MTG players