Army of Ruin

As the description says, you'll need to complete the stage with no earth trinkets (the leaf icon). This isn't too bad. You'll miss out on some really handy trinkets, like Magnifier and Shackles, and it also means you won't be able to evolve many starting weapons like Wolf's Fang or Necromancer Gauntlets or Toxic Stench. You can still focus on damage and knockback though, to help with the craziness of some later waves. Since you can't use Shackles to slow enemies and can't evolve the Storm Javelin to slow them, I recommend pairing this with Scout's Cap (10G) to go heavy on the knockback with Silver Bullet and/or Crimson Flask to keep the huge enemies at bay. Add in the Forbidden Sword, which is a massive game changer once maxed, and you'll be good.