The Ink Grenade is an infant Nemacyst Inker housed inside an Incendiary Grenade casing. When triggered, the Ink Grenade releases a thick, black and green, poisonous smoke for a short amount of time. The smoke damages enemies and obscures their vision. Prolonged exposure (5 seconds or more) to the smoke will down or kill an enemy character; a downed character is more susceptible to the poison and will die within a few more seconds of exposure. The Ink Grenade is used almost exclusively by the Locust Horde, particularly by Kantus.
The Ink Grenade has a number of uses, foremost as a powerful area-denial and dispersion tool. In addition to being hand-thrown, the Ink Grenade can also be used as a proximity mine by attaching it onto a surface or an enemy. When an enemy is "tagged" with an Ink Grenade, the enemy can escape the smoke by running continuously, as the smoke will stay in the area it detonated in; contrary to popular belief, the Ink Grenade does not continuously emit poisonous smoke but releases the smoke all at once until the smoke clears.
However, in Gears of War 3 when a player is caught in the Ink Grenade's blast, the player will be stunned whilst the gas damages them.
One use of an Ink Grenade is to deny an area to the enemy. This tactic is known to work in the Annex and King of the Hill game modes. The poison smoke forces the enemy out of the scoring zone, effectively delaying enemies from gaining points while making the scoring zone easier to capture by exposing enemies.
Another way the Ink Grenade can be used is to flush enemy troops out of cover and in hard-to-reach places. The poisonous smoke forces enemies to expose themselves by moving away from the smoke. Snipers are particularly vulnerable to the Ink Grenade, as they usually are located in places with little or no room to maneuver.
A good way to use the Ink Grenade is to plant a smoke grenade and ink grenade together. When an enemy player comes by, both grenades will explode (This can also work when thrown). The smoke will concuss them, leaving time for the Ink Grenade to down them. Since the Ink covers a large area, the enemy player will most likely die. This is very effective in multiplayer.
The Ink Grenade can also be set as a trap by attaching it onto a surface (such as a wall or behind cover). This tactic is especially useful in the multiplayer game mode Submission. The Ink Grenade can be used effectively against an enemy Meatflag Carrier, who suffers from a significant decrease in movement speed and maneuverability. The Ink Grenade can not only kill the Meatflag carrier, but also re-incapacitate the Meatflag, ensuring an easy capture when the smoke clears.
A special mention need be made of the map Hail, which has an Ink Grenade on it. This grenade can force enemies out of the very limited cover-spaces on the map when the Razorhail hits, effectively guaranteeing a kill. It is good in Annex or King of the Hill as enemies will be forced away and out of cover.
Tagging an enemy with an Ink Grenade can prove hilarious. Even before it explodes, after it is tagged on an enemy it damages them slightly in short pulses, guaranteeing that the first initial explosion will down them. The smoke will quickly overcome and kill the tagged foe unless they run constantly, and if they run near an allied unit, they wind up potentially suffocating their own teammates. Naturally, smarter enemies will try to stick close to you if tagged - make it a point to flee the scene after tagging a foe.
In Horde, an Ink Grenade is useful against a cluster of enemies. It is used by many players to combat Maulers, as they are slow moving when their shield is deployed. Their shield has virtually no protection from Ink Grenades. This also works against Clayton Carmine in Beast, with the added effect of making him drop the shield.
The Ink Grenade has other uses. It can provide cover, much like a Smoke Grenade, though this is often a waste of an Ink Grenade. Ironically, this can actually be an effective tactic for discouraging enemies closing to close combat, as the toxic smoke of the Ink Grenade can severely weaken any enemy foolish enough to charge through it, making them weak enough to easily finish off with weapons fire. Even worse, because the smoke obstructs vision far better than the Smoke Grenade, they risk Roadie Running into a wall and getting into cover while inside the cloud, which can kill an unprepared enemy with ease.
The Ink Grenade has one single drawback; it lacks any concussive blast. The Smoke Grenade's knock-down ability allows it to stun enemies temporarily, and the Frag Grenade, if it doesn't kill someone, has a similarly large knockback effect. Because the Ink Grenade does not have any explosive force, it cannot throw enemies around and does literally nothing to prevent enemies from fleeing its lethal mists, other than obscure vision. (A concussive blast was added to the Ink Grenade in Gears of War 3.)
The Ink Grenade can be very effective when planted as a proximity mine, if placed in the correct position. Try to place the Ink Grenade in an area that will be consumed by the poison gas, therefore prolonging its effects, but be careful not to place it in a way that the poison gas will affect you. The enemy will run through the area (or building) in an attempt to kill you, preferably with the Gnasher Shotgun or the Chainsaw Bayonet, detonating the Ink Grenade, and being forced to run through the WHOLE field. (This takes careful placement and practice in different areas)
A widely used solution to the above two statements is to pair a Smoke Grenade and Ink Grenade together as proximity mines. Plant the two grenades close to one another (enough so that they will both be tripped at the same time when an enemy runs past). When a player runs by, he or she will be knocked down and also be enveloped in a cloud of the poison - assuming that they weren't blasted to far away by the Smoke's concussion (and as such, it is advisable to use the combo in tight areas). By the time they recover from the blast of the Smoke, the Ink will have seriously injured or even downed them, making easy pickings for the opposing team.