Make some mobs cards have special abilites, its written at lower part of card, at a small text, below attacks.
Flip a coin at each attack used with cow. If heads, the attack does 5+ damage.
You should really try to make the cards be more interesting in their abilities. There are so many possibilities. Honestly, I think the way you designed it does not really fit with the theme (Minecraft). Focusing on just powering up a mob, when there is so much more to Minecraft, is really just only one small aspect of what it could be. I think a really cool way of doing this would be to have a large battlefield that includes terrain such as ocean, desert, forest, nether, and plain. Then players place mobs onto the field at a cost, and also do things (move/attack) at varying costs. Having redundant boosts makes it boring and weird/unrealistic (spider's bite based on random coin flips...?). You could even have special terrain changing blocks that you can use to "build" (change the terrain, like replace a dirt block with soul sand, causing everyone to move on their to be stuck one turn, essentially making that spot unusable). You could have resource 'cards' replace power cards as a source of energy. For example a pig wouldn't attack, it would provide a constant source of energy (so a pig card would be like a pig farm pretty much) for your hostile mobs to attack. This also adds an element of strategy to the game, because you can attack other people's resource farms, and you need to place them carefully. Although we don't want it to be too complex, we play Minecraft :tongue.gif:
If you want me to elaborate on how I think some of these ideas could work, I can.