You can also cage Nevinyrral's Disk and Soul of New Phyrexia / Aetherling to wipe the board on demand, or just equip him with Darksteel Plate to make sure he survives
Wizards is free to explore weird spaces, and, as demonstrated here, those spaces may occasionally do something really problematic
With a reliable way to repeatedly bring Ashen Rider into play, you can quickly start removing every permanent under your opponent's control, lands included
Queen Marchesa is a 3/3 Legendary Human Assassin that costs one generic, one Red, one White, and one Black mana, and has the Deathtouch and Haste mechanics
There are also plenty of ways to deal damage to your own creatures, either with direct damage spells, or cards like Forerunner of the Empire