Creatures are the most important cards in the Trading Card Game.
Creatures are summoned into the battle zone by paying for their level by tapping cards in your mana zone. They can attack your opponents creatures, shields or the opponent himself. Breaking all of your opponents shields and then attacking the opponent is how you win the game.
To attack with a creature, tap it, then select its attack target. You can only attack tapped creatures or an opponent's shield, unless effects state otherwise. Once your opponent has no shields left, you need to make one more unblocked attack to win the game.
Each creature has its own power, and it dictates whether it will be able to win the battle or not, if it battles another creature. It also has a race, which is vital to certain effects, and important for summoning evolution creatures.
Creatures that have been summoned usually cant attack in the same turn, with exception to evolution creatures and creatures that have the Fast Attack ability.
There is no limit to the number of creatures you can have in the battle zone.