The Viking is an elite unit that can be bought from the Unit Shop. It deals ranged splash damage against enemy air units, and can be used to eliminate units like the Mothership or Battlecruiser, as well as ball of air mercenaries. Vikings can switch to ground mode if necessary, where they deal single target ranged damage against enemy ground units. Ground vikings are good support for your army in numbers, but they shouldn't be bought if you only intend to use them against ground, because you won't get a good return on your investment.