The Mantis is sleek and light in construction. The gun's battery rests on three long legs and must cool off and release its excess heat after every shot, which exposes its weak point. The interior is vulnerable through a vent on the underside. A certain amount of damage to the interior will destroy the AA battery.
The plasma bolts fired by the T-27 are in a teardrop shape similar to normal plasma rounds and travel in a straight trajectory. One bolt is powerful enough to take down a Longsword. It was said that one Mantis is enough to "tear the Dawn apart," implying that an AA battery would be powerful enough to destroy or seriously damage a UNSC Frigate.
During the Battle of Meridian, the Covenant deployed eighteen T-27s in heavily defended batteries across the Cherbourg area of the planet. All eighteen were destroyed by the first HRUNTING/YGGDRASIL Mark IX Prototype ADS, earning the exoskeleton the nickname "Mantis."
The T-27 was used during the Battle of Voi on November 17th, 2552, when at least one battery had been deployed in the town of Voi in order to keep the UNSC forces away from the Portal excavation. The UNSC planned a low-level strike, using Frigates and Longswords, to attack the Prophet of Truth's Forerunner dreadnought which was resting on the Portal, which was thought to be the Ark by the UNSC at the time. Throughout the battle, the AA battery fired continuously, and managed to destroy at least one Longsword. Marines and John-117 eventually breached the Covenant resistance in Voi and destroyed the AA gun, allowing Lord Hood's ships to assault the Forerunner dreadnought.
AA guns were also used during the Battle of Installation 00, when the Covenant tried to construct them on the surface of the Ark to keep the UNSC ships above from reinforcing their troops on the ground. However, these batteries remained incomplete, as SPARTAN-117, with the assistance of several Orbital Drop Shock Troopers stopped their construction, allowing the UNSC Forward Unto Dawn to land nearby.
In the Halo 3 level The Storm, the main objective is to destroy the Mantis in Voi so that Lord Hood can start attacking the Prophet of Truth's Dreadnought. Two T-27s under construction also appear in the level The Ark.
- Halo 3
- Halo: The Cole Protocol
- Halo: The Thursday War (Mentioned only)
- Halo 4: The Essential Visual Guide (Mentioned only)