"You fall to keen the meaning of this, do you not? We have come for you, but in your ignorance you do not see it."
-Unidentified Stalker to Commander Brody
How Stalkers came into existence or where they originated is unknown. Even their actual designation isn't known- they are called Stalkers simply because they follow and track their targets for a significant amount of time before attacking. However, aside from this quirk, their near limitless strength, speed, and deadly skill, along with the super-flexible high-tech armor they wear, nothing is known of these creatures. They appear to the Epsilon's elite warriors, taking on the most important assignments and those that require a fine touch.
Stalkers are extremely intelligent, able to combat several highly trained opponents simultaneously and likely defeat them. They have exception strength and dexterity, and are renowned for their ferocity and deadliness. They possess high-tech armor that not only protects them from gunfire, but also can arm with an energy shield at any moment, even if the Stalker is unaware of the danger, to completely deflect a projectile before it even hits the Stalker.