Rooting off of what Hyroen said...if the opponent played a congeal + shockwave on the Scarecrow, would all that sacrificed HP go to waste with the instant kill?
Not sure about the element. Also don't really understand the card. What's the point of putting half your health into a gravity pulled creature? That health will still be lost whether your opponent attacks you or the scarecrow. That also brings up the problem of the scarecrow being insta-killed.
So you quintessence the Scarecrow, and so the gravity pull is cancelled. Then all of your permanents and creatures are still invisible unless they use rain of fire or something? And damage will then go to you, right?