I cannot figure out what costs would be fair for this.

Hee. So, in evoke mode it's like a sorcery-speed Swell of Courage but restricted to artifact creatures. is probably about right in order to let blue get that. As a creature... it's a heck of a lot more expensive than Shifting Wall or Phyrexian Marauder, but significantly cleaner than them as well. Much worse than Mikaeus, the Lunarch or the assorted green X creatures like Protean Hydra. But again, to let red and blue get a creature of this size... I think perhaps or would be fair. I feel is very expensive (ever since trying to play Meteor Shower in my very first deck).

BTW, the name Living Armor is taken.

Bah. Meteor Shower has nothing on Dwarven Catapult. Pay to cast Tremor? Yeah, why not.

I knew that was too much, but just seemed to cheap, and I didn't really want the evoke cost and the casting cost to be the same. just seems really expensive, though... I guess I'll put it at for now.
Also, I knew Living Armor was taken, I just wasn't feeling creative at the moment.

For an Evoke creature with a leaves-the-battlefield ability (which this is), CMC matching the CMC of the evoke cost is fairly common: Nevermaker and Meadowboon spring to mind, and I'm sure there are others.