I konw this may sound like a stupid discussion, but think about it first: Right now, witch of them is better for defense mission ? Frost' Snow Clobe has HP, small time of invulnerable, gains additional health during invulnerable (if it takes damage), receives 500% of Frost' base armor and slow enemies that get inside. Limbo' Cataclysm has no HP, shrinks over time, restores energy (2 per second when you are inside it), and damages enemies when cast, when it expires, and when they enter and leave it. Additionally, Cataclysm is now toggleable, so you can end it whenever you want. I personally believe that Limbo might be more useful in latter waves, but i don't know. Tell me what you guys think.