Fire Emblem: Gods of the Celestial Realm [OOC]

Flying units do not get terrain advantage. While unit 1 cannot drop the unit it rescued, unit 2 can move next to unit one, take the unit from unit 1, and then drop the unit all in the same turn.

So, the mage can attack the merc. The pegasus can rescue the mage, and then the archer can move next to the pegasus, take the mage and drop him.