Stalkers are reptilian, swamp-dwelling monsters from Hexen. Their first appearance is in Bright Crucible, the secret level found in the Seven Portals hub, and the first normal level in which they are highly prevalent is in Darkmere.
Stalkers are normally hidden beneath the surfaces of water or slime, but players can tell where they are by the occasional surfacing of their coils and the tell-tale rippling sounds in the water. They block the player's movement even when submerged, and this fact can also be used to locate them. Stalkers mainly inhabit swampy waters but have sometimes been known to inhabit clean water as well. Their attack consists of jumping out of the water, slashing the player, and submerging again. Shots from the Mage's Sapphire Wand stun them momentarily, and continuous fire from this weapon will prevent them from submerging until they die. They have 90 Hit Points.
There is also a second variant of the Stalker, refered to as a Stalker Boss by some. It is identical to the normal Stalker beyond the abilty to throw globs of corrosive acid at the player.