All signs of its genitals have been surgically removed, as have its ears and nose. Its limb extremities, the hands and lower legs, have been amputated and replaced with bolted-on metallic augmentations meant to reduce mobility. Stalkers preventing Alyx and Gordon from proceeding through the Citadel.The Stalker transformation process is performed at, where Combine scientists sever higher brain functions, experiment on the lobotomized victim in 'foul and depraved ways,' and embed a number of blackened nano-devices in the skin, 'slowly watching the victim lose all humanity.' As a result, the appearance and behavior of a Stalker differs significantly from those of a human.The body of a Stalker is grey, hairless, and heavily emaciated with very little muscle or fat tissue remaining.
