Originally Posted by
KaoruAoiShiho
Secondly, I really like the sacrifice mechanic. Yes it's imprecise for valuing cards, but it is an excellent way to manage resources. It encourages players to be aggressive on the field to keep your opponent's resource count low. It also prevents turtling.
It only makes sense that you're able to do this with units. Think about any RTS or strategy game. Good strategy usually revolves around the idea of using your units to disrupt the opponent's economy. Therefore we need a way for units to destroy opponent's mana, if mana is to be such a big part of it.