"We’ve recently heard reports about a mysterious new weapon in the hands of the Zerg. We’ve heard of battlefields being covered in a dense, blinding cloud, rending our guns all but useless, and of Battlecruisers escaping from battle only to be yanked back into the fray. The source behind these bone-chilling truths is the Viper, and we now have a full intel report on not only what it can do, but how."
The viper combines several vicious biological weapons to weaken enemy forces and give an edge to the Swarm. They are a specialized offensive-support strain, being perfectly evolved for battlefield manipulation, a role previously held by the defiler. The viper contains genetic material from the defiler.
The viper's tail is largely unchanged from the original defiler template. However, it has been evolved to allow the viper to maintain its balance and direction while flying, as well as steering.
What truly stands out, however, are the ingrown, crystalline spikes on the tip’s surface. These "crystals" emit a powerful pulse that the Viper uses to locate its targets with pinpoint accuracy. Its limbs, while formiddable in appearance, are crippled in terms of offensive capability, as the Swarm relegated them to the role of simplistic vice-grips. The protruding spikes are porous bone structures, able to pierce flesh and immobilize prey without inflicting lethal damage. and are directly linked to the creature’s lymphatic system. When on the prowl, the spikes exude a pheromone that makes the viper seem innocuous and non-threatening to its hapless victims.
Vipers store a thick microbial soup within their abdomens, and can spray the viscous mixture into the air whenever ranged foes approach, essentially nullifying the effectiveness of their armaments until they can move out of the cloying mist.
All vipers possess a prehensile proboscis—an elongated organ that serves as the viper's digestive system, and one that runs the entire length of the creature's body. Just as a frog uses its tongue to catch prey, the viper regurgitates its flexible intestines with great force in order to grab and pull a target towards its location. Enemies hoping to escape to high ground are quickly snatched from their dominant position by the proboscis, allowing the zerg to counter just about any tactical terrain advantage. This muscle is powerful enough to even draw a battlecruiser towards the viper.
When fatigued, the viper can siphon bioelectrical energy and nutrients from friendly zerg buildings, allowing it to quickly return to the fray. This is achieved by separating the ionic chains present in the hardened tissues of Zerg nest structures to produce a nourishing fluid. Said fluid acts as a catalyst for the plethora of microorganisms present in its bloodstream, which generate bioelectrical energy to replenish the viper’s stores.
Vipers were originally a type of primal zerg. With the need for a support strain apparent, the defiler template was revisited, and perfected with genetic material from an unknown species, preserving its core functions, but excising the defiler's lethality, which had been as deadly to zerg as it had been to the Swarm's enemies. Later, Kerrigan was able to evolve her own vipers from the mutalisk strain.
The viper strain of the mutalisk has the same statistics as a regular mutalisk (but aesthetically, it is different by having four blue wings), but can transform itself into a viper at a specific mineral, vespene and time cost.
Abduct costs 25 energy, Disabling Cloud replaces Blinding Cloud and prevents shooting from beneath the cloud entirely, Consume targets allied units, and the viper can directly attack air units, dealing bonus damage to armored units. The attacks deal 10 damage, +5 vs armored units, and have a range of 6 and a cooldown of 1.5. However, their attacks pale in comparison to dedicated air-to-air combat units, such as the viking.