Skar'wa-pattern Mantis
From Halopedia, the Halo wiki
The Anti-Aircraft Battery[1] is a Covenant Loyalist ground-based stationary anti-aircraft emplacement. It fires bolts of plasma that are extremely damaging. A single bolt can destroy a C709 Longsword-class Interceptor.
Appearances
Halo 2 E3 Demo
The AA Battery was first seen in the Halo 2 E3 Demo. When the Covenant invaded Mombasa, they stationed a handful of artillery pieces on the ground, which demolished UNSC buildings. Eventually, SPARTAN-117 and his group of Marines encountered one, and Sergeant Banks called in a Longsword air strike to destroy the stationary mortar. They fired plasma bolts similar to that of Wraiths and in indirect parabolic trajectories. A sizable difference is that in the demo the Anti-Aircraft Battery is larger than its Halo 2 and Halo 3 successors, being a spire-size when Longswords bombed it.
Halo 2
The roles of the AA Battery pieces as an active part of the Covenant assault were greatly downgraded in Halo 2, as the entire First Battle of Earth was downgraded. The Covenant apparently placed several artillery pieces on the beachheads of New Mombasa, but did not fire them.[2]
Halo 3
The AA Battery can be seen in the level The Storm and is the main objective of the level, which is to destroy it so that Lord Hood can start attacking Truth's ships. This time, the bolts that it fires are in a teardrop shape similar to shade and plasma rounds and in an almost straight trajectory. The plasma bolts are extremely powerful. However, in order to contain the cannon's efficiency,the battery must cool off and release its excess plasma in order to fire again. This makes the AA battery vulnerable to infantry and vehicle attacks(exploited by Spartan 117 and other UNSC participants during The Battle of Voi). One that is in construction can be seen in the level The Ark. Troops are often stationed on and around the gun to safeguard it from ground forces.