Hmm; unblockable; but your other stuff can't attack with it... and your other stuff can't block either; but that doesn't matter because the opponents can't attack?

Slightly too game winning, methinks. Would you allow "Opponent takes 6+ damage a turn, and you can't be attacked" for only 6 mana?

No, I wasn't thinking it through when I made this.

Hmm. It's like Blazing Archon but much more so. That was 9 mana and won in 4 swings; this is 8 and wins in 3.

Well, the archon doesn't have "Can only attack alone" and "Unblockable" the way this does.

Do those more than cancel out? I can't help but notice this has grown larger since my initial comment too...

I, for whatever reason, was thinking more of Iona, Shield of Emeria when I costed this. She has the potential to totally shut down your opponent's ability to deal with her for 9 mana. This doesn't do that, even if it does have a superior form of evasion.