- I really like my blue Heroes. How come they never attack?

You've got great taste in colors. However, if you're trying to beat the game by only using Blue Heroes,You're Going To Have a Bad Time (TM).

Now, why would that be? Whenever you draw a Mana Card from the Card Deck, it will be one of five elements. Each element activates the Hero Cards of its color.

Blue = Water
Red = Fire
Green = Earth
Purple = Dark
Yellow = Light

Your excellent Blue Team will only activate if you draw a Water Card... Unless you manage to get to 21. Super 21 will activate all the Heroes in your team, no matter what.

So having that hand of 20 of greens, reds and yellows will do you no good, unless you manage to either draw an Ace to take your hand up to Super 21, or if you use a Hero Skill to change the cards in your hand to the Water Element.