From Halopedia, the Halo wiki
The Banished employ a number of modified Banshees in their campaigns against their enemies.
Traditional Banshees are modelled after the 'sKelln, an aerial predator on the Sangheili homeworld Sanghelios. However, those variants in service under Atriox have been twisted from their original form, with design features and details inspired by an aerial predator from the Jiralhanae homeworld of Doisac.
Base Banished Banshee models are equipped with a fuel rod cannon for attacks against ground targets and rapid-fire plasma cannons for anti-air work, though can be upgraded with tracking plasma torpedoes for more effective air assault.
The Banished Banshees seen at conflicts on Zeta Halo in 2560 appear to take advantage of an entirely different model, seemingly that of the Type-26B Banshee. This Banshee, retrofitted by Kaelum Workshop, has been optimized for combat durability with it's thick armor covering the head and lining the wings.
Halo Wars 2
Banshees in Halo Wars 2 can be built by all Banished leaders at an Apex. Un-upgraded Banshees perform well against vehicles, but only okay against infantry, aircraft, and structures. Once the Plasma Torpedo upgrade is researched Banshees will perform well against aircraft. In Blitz Banshees cost 50 power and Unstable Banshees cost 90 power. Banshees can be infected by Flood Seeder infectors.
Changes from Halo Wars to Halo Wars 2
List of appearances