Pair Up

Double is a gameplay element found in Fire Emblem: Kakusei. It is similar to the Rescue command from previous games in the series in that you can temporarily command one unit to remove another unit from the map and carry them temporarily, but in Double, the unit who is carrying the other unit recieve stat bonuses rather than penalties. The stat boosts are determined by the class of the unit being ferries (for example, a Mage mainly raises Magic while a Knight mainly raises Defense) and the support level between the two units, as well as the actual stats of the supporting unit. On top of this, the two units can switch roles on command.

Double Bonuses
While doubling, the active unit gains statistical bonuses according to the following formula: Note that there is no bonus for HP.
 * Double Bonus = Inactive unit's stat bonus + Inactive unit's class bonus + Support level bonus