Ah, I think I get it. So it basically chews up creatures from each player and stores the total attack of eaten creatures. Then if a player cant sacrifice, they take that much damage...
So if you have more than 1 of these in play, does everyone have to sacrifice 2 creatures each turn?...
This is definitely unique and interesting. It may be a little too powerful with boneyards though, since you will automatically be getting weaklings to sacrifice every time your opponent loses a creature.
I think it may be a bit to powerful as CC in that manner, and thats not counting the damage output it will have.
Not sure how to balance that exactly...
Concept is very cool, but needs some work to keep it from being OP right now.
I think that the biggest issue here is that it is killing creatures indescrimenantly.
So to start looking at balance consider:
1) A creatures HP is an integral part of counterbalancing CC effects. If you can work in a way to make sure that larger creatures can survive the effect more readily than low HP creatures, you may have a good start to balance.
2) HP isn't the only way. Creature cost could be another.
In any event not every creature should have the same chance to die or it will upset metagame balance by over favoring decks that can spam lots of weak creatures or pack lots of PC.