Reusable blessing...needs skill cost increase to at least match that of blessing|improved blessing
I actually disagree. Assuming you're putting prophet back on top of it's owners deck, the cost is 
(summoning cost) + delay of turn and possible cc + 
/ for the ability cost + dead draw the next turn - utility value of reuse. Compare that with 3 /2 for blessing/improved blessing. I honestly think that even though prophet gives a reusable blessing, its intrinsic costs balance it, and maybe even make blessing/improved blessing more useful.
I agree with this. Spells often have a much higher cost than the equivalent creature ability because, even though a spell is a 1 shot deal, it is also much more difficult to stop than a creature with an ability.
Consider Antimatter vs Purple nymph, for instance. AM costs 8
while the nymph's ability costs 4
...
This card is further balanced by "dead draw" cost (aka card advantage cost). This is typically weighted at about 2
per card. So I think everything works out pretty well.
I actually think it would be cool to have this as a
creature with a
activation cost since we already have a
card with a
ability (sundial)...
It would also be a wonderful candidate for a hybrid
/
card. (see
http://elementscommunity.org/forum/index.php/topic,46114.0.html )
At any rate, its a very cool card idea. (Nice art too).
Good job!
