pretty much over the top OP.
Run a black deck with sacrifice and you can play any card in the game...
Boom sacrifice
->Miracle
->Fractal
->Any color Dragon
->Any color Nymph
->Any type of Shield
You need to set some limits, have more negative effects, increase the cost or something...
Example of setting some limits:
-The next card is free to play as long as the cost does not exceed 4 quanta
-Sacrifice card cost must be greater than 5
Example of some negative effects:
-Your max hp is reduced by half.
-You can no longer gain life. You lose 10hp a turn. (Yes it would prevent miracle from working)
-Half of your deck is discarded.
-You are now on Pandora.
Examples of cost increase: (Don't you dare that think just increasing the
quanta cost balances the card)
-Sacrifice a creature, weapon and pillar. Next card is free of cost.
-Sacrifice three black creatures.
-Sacrificed creature must cost more than 5 quanta.
-Tribute/Sacrifice takes 2-3 turns to complete sacrificial ritual. Ritual ceases if sacrificed creature is destroyed. Stronger creatures take less time to sacrifice.