The most important aspect of the game is the collection of monsters. Train, synthesize, and breed your monsters to make them stronger. Stronger monsters can take on stronger challenges.
Each element has its own strengths and weaknesses. If the element of the skill has an advantage over the opponent, you will do double damage. If the opponent has the element advantage, then your skill will only do 1/2 damage. Each skill also has its own element, and each monster has its own element type. If a monster’s element type matches the skills element, then the skill becomes 50% more effective.