Stalkers are easily identified by their gray colored armor that possess integrated circuitry for Cloaking in their Power Armor as well as their cyclops-like helmet with a bright red beam emitting from their "eye." They often use Radar Jammers to confuse their enemies to give them a chance to sneak up on them and are fond of Incendiary grenades. Their main weapon seems to be the Plasma Rifle and its Brute equivalent, though occasionally they are armed with Spikers or Maulers.
It is unknown how Brutes are promoted to this rank (possibly through the number of casualties they inflict on the enemy), but they are commonly seen acting as spies and bodyguards for Brute Chieftains. The Stalkers replaced the Stealth Elites of Halo: Combat Evolved and Halo 2 after the Great Schism.
The Brute Stalker does not appear in Halo 2 but is featured in two Halo 3 levels: The Ark and The Covenant, as well as being prominently featured in Halo 3: ODST, where they roam the streets of New Mombasa in small groups. They use their active camo to protect their Chieftains. They are especially dangerous in ODST because of the generally dark conditions they are encountered in; though it becomes very easy to see them once VISR mode is toggled on.
Stalkers often employ Plasma Rifles, Spikers, Maulers and Incendiary grenades in battle. The added advantage of their cloaking devices is balanced out by their below-average armor and health for a Brute (a feature they share with the stealth elite); a Brute Stalker is about on par with a Brute Minor in terms of shielding strength and health. On Heroic difficulty it takes 24 assault rifle bullets to kill a Stalker; 8 shots to bring down their shield, and an additional 16 shots to kill them.
Once you spot the distinctive visual disruption caused by their active camouflage, use your weapon and melee them. They will be stunned and temporarily visible. Follow up with more melees until they're dead. It is advisable to only attempt this when there are no enemies nearby. Charging a Plasma Pistol and firing at the Brutes' movement shimmers will usually strip their power armor, making them visible. Also, they will be temporarily visible when they throw their Incendiary grenades.
If the Brute goes berserk, dodge the physical attacks and finish them off with a melee or headshot. On higher difficulties, it is advisable to use grenades, as they will blow their cover, and they can be quickly finished off by an automatic weapon. Watch for enemy fire and destroy any Radar Jammers you see deployed on the ground. Using the Power Drain will also strip their armor off, resulting in them being visible and having almost no shields. If the Stalker is standing on a glass floor, its feet should be visible. It is also effective to use a Spiker or Needler as the spikes are visible when stuck in the Brute. Defeating them is the easiest way to get incendiary grenades.
In Halo 3: ODST, fighting Stalkers is much more straightforward. You are able to see them as yellow outlines in VISR mode, however, the outline color matches that of the terrain outlines, so they can theoretically still blend in if you don't watch yourself. Like all Brutes in ODST, they also sport full energy shielding that can withstand twice as much damage from projectile weaponry compared to in Halo 3. Besides these differences, it's mostly the same. One last thing is that they don't seem to know that you can see them, they may stand out in the open thinking that their camouflage prevents you from seeing them. In reality, it just makes them a big target.
- Todd McFarlane released an action figure of a Brute Stalker for its second series of action figures. It features two Spikers and a removable helmet.
- It is easier to spot a Brute Stalker by looking for its feet, as their cloaking reveals their feet more than any part of their body.
- On higher difficulties, a single Brute Stalker wielding a Brute Shot can be found at the second highest level of the Cartographer entrance on The Ark, just after defeating the Scarab.
- On the level The Covenant, the Brute Stalkers at the second tower guarding the Brute War Chieftain can be easily spotted by a glitch in which the player stands behind the glass wall right after arriving in the elevator which "cuts" their active camouflage in half where their bottom half is revealed and the rest of their body remains camouflaged.
- In the official Halo 3 guide it states that there is a 'Brute Tracker'. No such Brute has been found, so it may be that they were cut from the game, were going to be a higher ranking variant of Stalkers, or that Tracker was just the Stalker's original name.
- Brute Stalkers can be found alone or in pairs roaming the streets of New Mombasa in Halo 3: ODST. Their Active Camo is compromised by the VISR which outlines their body despite the camo.
- Reverse-engineered Brute Stalker technology was used to construct the Mjolnir Powered Assault Armor/Stalker.