Locust Horde

Grubs are the basic infantrymen of the Locust Horde. They generally carry Hammerbursts (burst fire rifles) and are about the same size as the well-armored COG soldiers. They are also known to carry Lancers that the COG soldiers carry and occasionally a Boltok Pistol or Longshot Rifle. They are one of the most common enemies that you will face in Gears of War. Grenadiers are very close to grubs except they carry Bolo Grenades and Gnasher Shotguns.  Grenadiers are known to charge up to the COG Soldiers to take full advantage of their shotguns.

Wretches are small four-legged Locust with razor-sharp teeth and claws. They specialize in hunting their pray and leaping high into the air crawling on walls and pouncing on their victims doing a large amount of damage. Wretches generally stay in groups, so if there is one Wretch, there are probably going to be a lot more. There are also special kinds of Wretches in Chapters 3 and 5 in the first Gears of War. These wretches act as any other except that they explode once they are killed due to prolonged exposure to Immulsion, so it's important to take them out and immediately move out of the way.

Boomers are the juggernauts of the Locust Horde. They look like an oversized grub carrying a rocket launcher. Boomers have a ton of health, taking around three headshots with the Longshot or an entire magazine to the head with a Lancer. Boomers also have a very powerful melee attack, to keep those who would tag them with a grenade at bay. Boomers do have a weakness though; they are incredibly slow. They can barely walk giving you plenty of time to take them out before the reach a range where you can't dodge their Boomshot. They also will say "Boom!" right before they fire so you have an indication of when they will shoot.  The second Gears of War game has different variations of the Boomer, each wielding melee weapons that will kill the player in one hit.  One of these variations also has a Boomshield.

Left is a Mauler, Right is a Grinder

In Gears of War 2 there are new units similar to the Boomer called Grinders, Butchers and Maulers. Butchers wield large cleavers, the Grinders wield Mulcher gatling guns and shout "Grind!" before unleashing their gatling guns into you. Some variants of the Grinder will wield flamethrowers, the Maulers wield explosive flails and shields.

Theron Guards are considered the elite of the Locust foot soldier. They wear special armor and generally carry either a Lancer or a Torque Bow. They are generally more accurate than the rest of the Locust that use guns and need to be watched carefully when sporting a Torque Bow since those are one-hit kills.

Kryll are the smallest of the Locust but perhaps the most deadly. Kryll only come out during the night since UV light burns them to vapor. Kryll are dangerous because they are in groups of thousands that will eat anyone and anything within seconds, so don't go into the dark unless you want to be eaten alive. When faced with Kryll the player has a couple of seconds allowed in the dark before the Kryll start coming.

Brumak are literally walking tanks. Brumak are large Locust that have cannons strapped to their arms and back. In the Xbox 360 version you merely have to get on an APC before a Brumak arrives at the battlefield, while the PC version has you fight a Brumak on foot. However, in Gears of War 2, you fight Brumaks many times in tanks which allow them to be quickly disposed of by cannon fire. You may also ride a brumak allowing you to crush part of the locust base and make you finally feel what it is like to be a Brumak, or at least ride on one.

Corpsers are a spider-like Locust that fight using their many legs. It's size rivals that of a Brumak's and uses it's legs as a protective barrier. The player fights a Corpser at the end of Chapter 3 in the original Gears of War and has to shoot the belly and mouth in order to defeat it. It appears in other parts of the game and is powerful enough to burrow giant holes in the ground

Berserkers are about the same size as a Boomer and are incredibly strong. They dash and swipe at their enemies instantly killing them, making them a force to be reckoned with. Berserkers are unique in that they are blind and use sound and smell to track their enemies. Any movement that is faster than a slow walk alerts them immediately  and makes them charge breaking walls and pillars in the process. Berserkers are also immune to every weapon save the Hammer of Dawn. Beserkers are found in Chapters 1, 4 and 5 of the first Gears of War. They are however nowhere to be found in Gears of War 2.


Kantus

The Kantus are the Locust priests. They can use chants to revive dead teammates and to command their allies to attack. They wield a Gorgon Burst Pistol and poison grenades. They generally stay in the back of the group so the others can do the damage while the Kantus keep their comrades from being killed. The Kantus are the ones teams should focus on due to their revival powers.