Primal zerg

"Behold...Zerus! Birthplace of the zerg. Here the zerg evolved. And here the Dark One altered them. Those left behind are the primal zerg. They fight. They kill. They evolve."

- Zeratul

The primal zerg are an alien species from the planet Zerus and serve as the original zerg template race. Having resisted the control of The Overmind, they are separate from the Zerg Swarm, both physically and psychologically.

History
Main article: Zerg history

Ancient History
The zerg emerged from the first spawning pool. The zerg fed on each other's essence, gaining strength, a practice that was carried out as they emerged beyond the pool and assimilated Zerus's other lifeforms.

As the xel'naga uplifted the zerg, Amon intended to use the zerg for his own purposes. However, the independent nature of the zerg necessitated the creation of a hive mind to direct the species in order to make them more controllable. As a result, the Overmind was created, with many zerg falling under its control. This event being witnessed by the creature known as Zurvan.

After turning on the xel'naga, the zerg under the Overmind departed Zerus. At this point, the zerg went down two different paths&mdash;those of the Overmind were known as the Swarm. Those who had escaped its control remained on Zerus, becoming known as the primal zerg. Here, they continued to prosper, hunt, and evolve.

Second Great War
Centuries, if not millennia after the Swarm's departure from Zerus, the primal zerg encountered their counterparts. Sarah Kerrigan, after being de-infested by a xel'naga device, sought to find a new means of increasing her power. Whilst aboard her leviathan, she met with the Dark Templar Zeratul who revealed to her the existence of Zerus and of the primal zerg who were needed to transform her once more.

Upon arriving at Zerus, she awakened Zurvan and battled the primals, who intended to kill the "corrupted" zerg. Kerrigan achieved her primal form and defeated other primal leaders. She departed Zerus with allied primal zerg, including Dehaka who followed in the hopes of acquiring new essences.

During Kerrigan's attack on Korhal, the Terran Dominion activated the Psi Destroyer, a superweapon which killed zerg through their hivemind. Because the primal zerg were immune to its effect, Kerrigan dispatched Dehaka and his pack to weaken the enemy. Finally, the zerg destroyed it.

Physiology
"I do not need a wall, I will evolve armor. I do not need a weapon, I will evolve claws. The toolmakers might create something stronger than your armor and claws. Their tools stay the same. I collect. I change."

- Dehaka and the Queen of Blades comparing primal zerg abilities with those of terrans

Primal zerg have the ability to take essence from their foes, consuming their flesh and through it, their DNA. They are in a constant state of evolution, incorporating beneficial traits from their victims. Such traits can become manifest in a short amount of time, ranging from seconds to hours, or a few days. Through this, the primal zerg were able to mimic numerous Swarm strains, while retaining their own physiological markers.

While the strains of the Zerg Swarm often bear an insect-like appearance, primal zerg bear more resemblance to reptiles, and in some regards, mammals.

Psychology
"No allegiance but to self. Kill or be killed."

- Zurvan

Unlike the Swarm, primal zerg lack any psionic connection to one another. Because of this, they consider Swarm zerg to be "corrupted," and to fall under such an influence was regarded as a "terrible fate" by Zurvan. It is a difference that was a point of contention for many primal zerg, despising their Swarm counterparts for it. Because of their lack of shared hivemind, they are immune to the effects of some devices that would otherwise cripple Swarm zerg.

Primal zerg can operate in packs instead of broods. Their philosophy/culture is effectively Darwinian in nature, operating on the principle of survival of the fittest. It is loyalty to strength that determines their allegiances, or the choice to break them if the opportunity presents itself.

Primal Zerg Pack Leaders

 * Brakk
 * Dehaka
 * Kraith
 * Sarah Kerrigan (by virtue of position, biologically a terran/primal zerg hybrid)
 * Slivan, the Eternal Mother
 * Yagdra
 * Zurvan, the Ancient One

Trivia
Samwise Didier did concept art for the primal zerg while Phill Gonzales did unit modeling. Most of the primal zerg variations were based on dinosaur species he enjoyed as a child.

The concept of the primal zerg might be left over from the development idea of the "metamorph", a zerg strain developed by Kerrigan and Abathur that could direct its own evolution.