As this is my first post, I hate to make what may seem as a negative comment, but I hope that my argument comes across as reasoned and reasonable.
First off, let me say that I find myself enjoying this game more than I thought I would. I am a big Magic fan, of course, so I am intrigued by the approach Element takes. I also followed Magic development closely for several years, so I'm well read on game mechanics and the idea of balance in a game. That being said, I'm still no expert, and certainly am not brave enough to put any creation of mine into the public eye!
I've seen a couple of cards in my short experience that strike me as horribly unbalanced. Immortal is one of them. There is also a sword that can't be stolen or destroyed, but that's really what I'm getting at. Any card that is completely untouchable can quickly become a problem in a game, where suddenly that card becomes the only win condition because it can't be beaten.
I feel there is also a misnomer to the text "targeted." Targeting is easily understandable, and has a certain meaning. In this case, to specifically single out one target for a specific effect. However, an untargetable creature or permanent should still be subject to global effects, since they don't single anything out.
So, my comment here is twofold: I feel the wording should be unequivocal when it comes to games where the text has a direct meaning to the gameplay, and no piece in a game should be completely untouchable once it is in play, even if it's only in a couple of obscure ways.
Hope I didn't come across as a whiner. I would just like to give my input in the hopes of helping someone develop a truly interesting game.