- "It's about to get hot!"
- —Marcus Fenix, throwing an Incendiary Grenade
The Incendiary Grenade is an improvised explosive device created by Stranded forces. It is a simple device, consisting of a bottle of Imulsion, with a burner on the end. Essentially, it is a bolo-style Molotov cocktail.
During the destruction of Halvo Bay, Incendiary Grenades were fired from the Grenade Launcher on the back of Karn's Shibboleth during the battle between Karn and Kilo Squad at the Plaza for the Tyran Dead.
The Incendiary Grenade has a chained handle like all other Bolo Grenades, but consists of little more than a bottle of Imulsion, with a burner on the end. Unlike the other grenades, however, it explodes immediately upon impact, even on ceilings and walls. It serves a similar purpose to the Ink Grenade; area denial. It can also very quickly down, and possibly even kill, enemies wielding heavy weapons, since they would be unable to avoid the grenade. It causes significantly more damage than the Ink Grenade, and is less noticeable once detonated, with the small flames quickly concealed in certain maps (such as the sandstorm in Trenches). Incendiary Grenades also spawn in pairs, like Frag Grenades, which is another benefit over its counterpart.
The Incendiary Grenade also boasts the ability to instantly kill an enemy on direct impact, igniting the target in a manner similar to the Scorcher Flamethrower. This means that, as a last resort, the Incendiary Grenade can be used by those with a good aim to take out close range enemies, although this is a risky and difficult tactic.
Like other grenades, it can be "tagged" to walls to mark off certain areas to enemies. This could be used near weapon spawns, forcing enemies to back away, and alerting teammates of their position. However, the Incendiary Grenade produces a noticeable flame when tagged, so it can be easily taken out if not concealed. However, an effective tactic is to lure an enemy towards you by shooting at them, making them unaware of the grenade.
Incendiary Grenades (unless bought) can never be looted from an enemy in Horde mode. This is due to their wielder, the Savage Grenadier, never appearing in Horde. It is unknown why the Flame Grenadier does not wield them, as he specializes with fire.