This thing is a surprise waiting to happen, mostly because of the decks it will be run in. I can easily see this being the win-con on some abhorrent Wall deck and it will be great. When people think of Walls, they normally think of things like Wall of Omens or Wall of Blossoms, you know, Walls that have some use outside of being a blocker. This card, however, enables other Walls to be as useful by allowing for the creation of big stompy things. Shield Sphere? Why yes, I'd like a 6/6 on turn 2. Wall of Junk? I guess a 7/7 on turn 3 is okay. Wall of Shards? More like "Wall of Better Phyrexian Soulgorger". Now, I know the creature created doesn't have evasion and can easily be killed, but aren't those the same complaints that can be made about Tarmogoyf? There are only two big issues with this card. First is that it is based around toughness instead of power, so if you're going to use it to its full effect, you'll need either early Walls to be able to hold out until you've got big creatures. But even if you don't have huge creatures or Walls, it can be used as a cheap mini-Cackling Counterpart for your biggest creature on your turn, which isn't all that bad on its own. The second issue is the timing. As a sorcery, you can't use this as a combat trick nor can you use it to give you creature pseudo-Haste by having it ETB on an opponent's end step. Despite both those issues, I really like this card. I expect to make a deck around it in the near future.
Pros: Mini-Cackling Counterpart on your toughest dude
Cons: Sorcery speed, based on toughness