Given that this occurs when the card is Played rather than as a continuous effect, it might be a little easier to balance... At the very least, it will make fraca-spark abuse trickier than with a pervasive nightfall like effect.
This seems wayyyyyyyy too powerful. A mass +2|+2 buff for a whole field of creatures?
Not only is it a mass buff... but it's a mass debuff for enemies? does 2 damage to all enemy creatures?
Plus you can rewind it... so it's a reusable buff? over. and over. and over. and over again with an eternity?
Plus 3 . Blessing costs 3 unupped and only buffs a single creature for +3|+3
way too powerful.
^
Even without the health bump to allies, having both ally buff + enemy debuff in a single card is going to be tricky to balance well. Particularly since it is in element with the staff of eternity, which would allow you to effectively spam it
Ex: flying Staff of Et. + SoR + this -> +6 attack to all allies and -3|-3 to all enemies...
Cost = 3 cards + 6
+ 3 * 4
+ 3
... = 3 cards + 18
+ 3
.
Thats just 1 turn of course. With SoR flying staff, you can repeat the summoning every turn for +2|+0 to ally and -1|-1 to enemies.
The debuff on a stick wouldn't be too bad alone, but the mass buff on a stick could get dangerous (considering it effectively costs 4
after initial setup)
Seems a little too much to me.
I think having both a buff and debuff effect at the same time is a little too much though. Maybe make it one upped and the other unupped or split into 2 different cards.
Finally, it isn't stated in notes, there are a couple issues to address when lowering attack values:
-How does this interact w/ antimatter?
-Will this be allowed to cause enemy attacks to go negative?
-What if they are already negative... will it drop them lower?