"In the Aion beta, Spiritmasters can summon four kinds of spirits, each based on one of the core elements: earth, wind, fire, and water. At Aion's release, we will introduce a fifth spirit. This new spirit is specific to a character's race. Asmodian Spiritmasters will be able to summon a spirit that is a combination of the elements of fire and earth, and Elyos Spiritmasters will be able to summon a spirit that is a combination of wind and water. Each spirit has different abilities. It can be challenging at times to recognize which element would be best to call on, and it is a mark of a player's experience in the class to become skilled at this decision. Using the right spirit at the right time can be the difference between winning or losing a battle."
Check out the full interview for more information.