Before reading the specific information on every unit’s and building’s upgrade path in the next chapter, it is important to understand what upgrades offer in a more general sense. Usually, a unit upgrade provides a specific ability (accessed via 
) or function (such as a faster-rotating Turret for a Scorpion), but each upgrade also adds a +25 percent statistics boost to damage inflicted and resisted. Most units have three (or two) upgrades providing specific combat enhancements to purchase when your Tech level is sufficiently high enough. However, there is one exception: Covenant leaders’ upgrades grant a 200 to 300 percent upgrade in combat performance and defense.
Scorpions, Hornets, Wolverines, Cobras, Vampires, and Wraiths are already “statistically upgraded” once prior to arriving on the battlefield. Vampires are already statistically upgraded three times prior to arriving on the battlefield. Vultures are already upgraded with additional firepower, while Scarabs appear fully upgraded.