Did Vortiguants come from Xen? No, they were enslaved there by the so called Nihilanth. Describe what a Vortiguant looks like (Detailed description) The Vortigaunt's are dark green skinned aliens with hunched backs, hooves, small claws and four red eyes. They also have a third small arm in the center of their body, used for eating. They have no lower jaw, thus they have a lisp. What were they while on Xen? They were enslaved soldiers. What is the Vortessence? (Detailed description) The Vortessense is the power that is within the Vortigaunts. Ohter creatures have it too, but the Vortigaunts are the only ones familiar with it and are the only ones that can use tap into it. The powers they have are such as; healing, resurrecting near-death organisms (show in HL2:EP2, with the use of the larval extract), teleporting, welding objects, illuminating light, beam attack (your standard green lightning bolt attack.), shockwave attack (hl2:ep2). What were they doing in Black Mesa? They were sent there via the Resonance Cascade by Nihilanth, ordering them to attack Earth.
Do you agree if you get dewhitelisted from the whitelist you're allowed to reapply once then you will have no chance of getting the Vortiguant whitelist do you understand? Of course.