Although not directly used in the game, categories help classify units and allow users to know how they can acquire a specific unit.
There a four different categories of units:
- Regular units can be acquired normally through different types of summons and quests, depending on the unit.
- Limited units are special rewards from limited-time promotions.
- Event units are each related to a special event. Normal event units can usually be found in quests and special event summons while U-Normal and Rare can only be found acquired those summons. You can also obtain Normal, U-Normal and Rare units from previous events through special event summons. S-Rare and U-Rare units are rewards for the top-ranked players in each event.
- Special characters are units that can be acquired through platinum and major summons. They hold a special power for the related event against the event boss (usually 10x ATK for Rare and 20x ATK for S-Rare and U-Rare). Special characters from previous events may also be obtained through platinum and major summons.