Adding 2 mana in a combination of colors enables lots of multicolor cards like Omnath, Locus of All, and Niv-Mizzet Reborn which would be far harder to use otherwise
The Modern Horizons set symbol has Emrakul's head over the horizon diamond
I play Porcelain Legionnaire in more red decks than white decks, but this functionally colorless creature continues to stand out on rate from Pauper Cube all the way to Vintage Cube
Gyruda also fails to work in the main list of a 60-card deck, as its mana value of 6 makes it an unwieldy creature to fit into anything that's facing faster decks, such as Eldraine Gruul and Dimir Rogues during Ikoria's time in Standard
Additionally, the 10 mythic rare Special Guests cards also received the borderless treatment
Preferably, they have anti-botting measures or invite systems