The issue with Empty the Warrens against combo decks is that you typically give them one or two turns before they actually take lethal, meaning they have ample time to assemble and use their combo unimpeded
That's more than either color alone could do, making Bedevil a strong option in Rakdos-colored decks
Enter Soul of New Phyrexia
[44] Colors of Magic Most cards in Magic are based on one of five colors that make up the game's "Color Wheel" or "Color Pie", shown on the back of each card, and each representing a school or realm of magic: white, blue, black, red, and green
This thing will basically always give you an immediate impact that is powerful and then if it sticks around the game is well and truly over for your opponent 5/5 worth of stats for 4 mana is a great starting point, and the Gutter-Dweller also happens to be able to grow and draw you cards using the expendable bodies he gives you