A Union is a small set of units you control in combat that is led by its single Union Leader. A minimum of one unit is required to start a Union, and the max units that can comprise a Union is five. The maximum number of Unions that can be created is also five. The Union Leader must always occupy Slot Number 1, any other member thereafter can occupy any slot.
A minimum of one unit in one Union is required by the game. In the Xbox 360 version, this can only be Rush since he can never be taken out.
A Union is comprised of three things: its units, Union Attributes, and Formation.
Each Union has four attributes that determines its effectiveness in combat:
- ATK - Determines how much physical damage the Union can deal to an enemy
- DEF - Determines how much physical damage the Union can mitigate
- MYS - Determines how much mystic damage the Union can deal to an enemy
- M. DEF - Determines how much mystic damage the Union can mitigate
These values are calculated by taking in each individual unit's associated Attribute and then averaging it. So if the Union comprises only one unit with an ATK value of 100, the Union's total ATK value will be 100. On the other hand, if the Union is made up of two units with differing ATK values, one being 50 and the other 19, then the Union's ATK will be 34.
These four Attributes come only from a unit's weapon(s). This applies regardless of whether the unit is in a Union alone, or with other units.
Dual Wield and Quad Wield units are treated slightly differently depending on the version. On the X360, 50% of the unit's offhand ATK and MYS is added to the main hand before being averaged with the others in the union. On the PC, all 4 equip stats are averaged before being averaged with the other units in the union.
A Formation is how the units are actually situated in battle. These bestow different Attribute bonuses and/or penalties depending on the Formation chosen and unit placement.