There are 2 differents factions.
At the start of the game you will be able to chose the faction where you desire to start your journey: Sentinel: the warriors of the light, they fight for the glory of their kigdom fight the force of the scourge and the devils of the lands of Zendynamar. Scourge: the warriors of the dark, commanded by the emperor Zelsius, they want to conquer the world of Zendynamar and they'll fight everybody to get their objectives.