Stalker

Stalkers are encountered much later in the game, and are one of the most difficult enemies to deal with in the game. They use night vision goggles, have a large 360 degree sense radius, and are equipped with wrist lasers which will generally kill the player, gruesomely, in two hits(without any health upgrades).

Tactics

 * Stalkers must be disabled before they can be dispatched with a Stealth Kill or non-lethal takedown.
 * Caltrops, Distraction Flares, and Dusk Moths are all effective items that can disable a Stalker.
 * Alternatively they can be dispatched lethally in one shot via Friendly Fire, Object Kills or other environmental hazards (indirect kills) and attack items such as: Ravenous Insects, Upgraded Hisomu Terror Darts, Spike Mines, and Fungal Spores.
 * It is possible to disable Stalkers temporarily by throwing a regular dart after they have been terrorized by a Hisomu Dart. They will not commit suicide after they recover from being disabled.
 * Engaging in direct combat is also possible, being able to disable them with repeated melee attacks; however they're incredibly resilient and can quickly dodge incoming attacks and counter-attack. They are also rarely encountered alone. Note that engaging in direct combat will cause the Stalker to become alert, causing you to lose your No Alarms Raised Bonus at the end of the mission.
 * As they are equipped with the same head-gear as the Gas Mask Guard, they are vulnerable to Distraction Flares and immune to Smoke Bombs.

One thing that makes them so difficult to deal with is their unpredictable movement patterns; they can climb walls, use vents, and utilize grapple points like the ninja. They also move very fast, will follow the player for quite some time, and are hard to shake off your trail. However this can make it easy to lead them into traps, but usually requires the player to be discovered first, which raises alarms and penalizes your score by -800; however using poking tactics (such as letting them notice your presence or throw Darts to get their attention) can allow the player to attract them to traps without being detected.