From Liquipedia Starcraft 2 Wiki
This article is for the Multiplayer version of this unit, for the Wings of Liberty Single Player version see: Viking (Wings of Liberty Campaign).
|Description||Versatile support flyer loaded with strong anti-capital air missiles. Can switch into Assault mode to attack ground units.|
|Cost||150 75 42 2|
|Defense||125 0 (+1)|
The Viking is a strong and versatile Terran unit with both anti-ground and anti-air fighting capabilities. The Viking is created from the Starport and can support a Terran army from the ground or in the air.
The Viking is the anti-air unit of choice for many Terran players and indeed, one of the strongest AA units in the game. Its 9 range overwhelms all other air units.
The Viking's mechanic to switch from ground to air on the battlefield gives it great maneuverability and tactical options within the Terran arsenal. The two abilities that the Viking have are Fighter Mode and Assault Mode. Fighter Mode changes the Viking from ground attack unit to an anti-air flying unit. Assault Mode changes the Viking from anti-air attack flying unit to a ground attack unit. In this mode the Viking may be loaded into a Medivac.
In Fighter Mode you can form a Viking Flower by micro'ing them on a single point to hide the number of Vikings you have. The Flower will swiftly take down almost any air unit that enters the Vikings' range of 9, the longest of all air units in the game (except for the Tempest). A Flower is however extremely vulnerable to area-of-effect weapons such as the Thor's anti-air splash attack or an Infestor's Fungal Growth. Although Blizzard attempted to remove this feature during patch 1.3, a slightly extended procedure achieves the very same result .
Note that the Viking always benefits from Ship Weapons upgrade, even in Assault Mode.
The Viking is considered an aerial unit during the full three seconds of transformation. This makes it quite good at hit and run tactics against ground units that can't hit air, as the Viking can liftoff as soon as they are in danger. The same cannot be said about fighting against air units that can't hit ground, as the Vikings will get pelted while they are trying to land.
Because of this, it is actually very dangerous to keep your Vikings on the ground when the opponent has mobile anti-air units: If the opponent flies in his units, your Vikings will either have to stay on the ground, vulnerable to land units, or liftoff, taking a beating during the transformation.
 Competitive Usage
 Vs. Protoss
Vikings are mainly useful for infantry support, as they can take out Colossi from a long range. They can also be used to deter Protoss air units, as Vikings out-range Void Rays, Phoenixes and Carriers (when Interceptors have yet to be launched). On an equal supply basis, Vikings will be able to take out Void Rays and without micro will go relatively even against Phoenixes and Carriers.
However, Vikings are primarily used to kill Colossi. The number of Vikings to get should depend on the number of Colossi your opponent has. However, you may want to get enough Vikings to take down Colossi in X number of shots.
Assuming no upgrades, Vikings deal 10 (+4 armored) x2 damage per attack to air. Therefore it takes 5 attacks to almost deplete their shields (140 damage). After that they deal 13 x2 damage to the hull per attack (colossi naturally have 1 armor). 6 attacks will deplete their shields and deal 16 damage to the hull. After that it takes 8 shots to deplete their hull health (184 remaining, 26 damage per shot), for a total of 14 shots.
To 3-shot colossus, therefore, you need 5 Vikings.
To 2-shot them, you need 7 Vikings.
To 1-shot them, you need 14.
 Vs. Terran
In TvT, they are used to hold off the opponent's Vikings, Banshee attacks or Battlecruisers. TvT often revolves around getting Siege Tanks and Vikings very early on. While the Tanks do the most of the damage, the Vikings give increased sight so that the Tanks can utilize their full range.
Air dominance is a very important aspect of TvT, as whoever has control of the air will get both the range-bonus for his Tanks, as well as the ability to safely mix Banshees and other air units. In the early-mid game they can also be used for harassing the opponent's mineral line, and in some cases they can be well used as a part of the Terran's ground army. Landing them on top of an opponent's sieged Tanks is also a popular technique. Another option is to land them on unreachable cliffs, to fire at troops underneath them, especially when the enemy doesn't have air units providing sight.
Vikings are often a key aspect of TvT all game long as there is no clear counter for it. Thors can be used to keep Vikings from giving sight to your Siege Tanks, but as Thors are best against light air units, they don't kill Vikings very easily. Battlecruisers are tentative option in the very late game, but as the Vikings have a larger range, and cheaper, faster building properties, BCs without Yamato Cannon usually are no match.
 Vs. Zerg
Vikings can play both harass- and army-roles in TvZ. Apart from scouting, small numbers of Vikings can be used to kill off Overlords to both harass and to clean up creep drops. Since Overlords are armored, Vikings get an extra attack bonus while sniping Overlords.
Vikings aren't too cost effective against Mutalisks, but they can be used as a deterrent against Mutalisk harass, thanks to their long range.
In the late-game, Vikings are very effective against Corruptors and a pure hard counter to Brood Lords. However when Brood Lords are supported by Corruptors and Infestors care must be taken because exposed Vikings can be caught by Fungal Growth. Therefore to trade cost-efficiently the Vikings should be spread out to reduce the splash damage. Additionally, Kiting helps to fight Corruptors due to the Viking's superior range.
Viking's quotes (video and sound) - Youtube video.
 Patch Changes
|Patch 1 (version 0.3.0.14093)|
|Patch 6 (version 0.8.0.14593)|
|Patch 14 (version 0.16.0.15580)|
Ground damage decreased from 14 to 12.
Lost Viking - Arcade minigame playable in the single player Wings of Liberty campaign.