http://www.starcitygames.com/php/news/expandnews.php?Article=7552 Thing is, I think it's a Helm of Obedience (see "Six Beginner's Delusions You Meet in Heaven").
Ah, aren't keywords lovely?
First, by nature, this goes in "The Deck," so costing five mana and being Green mean it has to make my jaw drop way lower than Manila's Maui Taylor.
Jaws still okay?
Okay, as I was saying, that jaw-strain wasn't caused by All Suns' Dawn at all. Dawn is dead until you can start using it as an extra-strength Regrowth, so the question is how long it's dead in hand.
The mana cost is only the first tempo problem. Regrowth effects are inherently slower because you have to wait for the card you want to hit the graveyard. In Dawn's case, you have to wait for a mix of them, in different colors. Simply, by the time that happens, it isn't that much more game breaking than the bombs you already have, and those and Skeletal Scrying are dead for much shorter periods.