From Halopedia, the Halo wiki
Spirits are armed with a singular rotating, low-mounted heavy plasma cannon, located directly below the cockpit of the dropship. This variant unlike the Type-25 Spirit has a gravity lift straight into the cockpit allowing for quick retrieval from a battlefield.
Towards the end of the Harvest Campaign Covenant forces used Spirits against the crew of the UNSC Spirit of Fire. The Covenant also utilized Spirits against UNSC forces and civilians alike during the Battle for Arcadia where one retrieved Arbiter Ripa 'Moramee after he kidnapped Professor Ellen Anders. During the Battle of the Etran Harborage Covenant forces used Spirits not only against the crew of the Spirit of Fire, but also against the Flood and Sentinels. During the Human-Covenant War at the Battle of Mombasa, Type-28 Spirits were deployed to recover the Conduit.
After the end of the Human-Covenant War T-28 Spirits were used by Merg Vol's Covenant during the Battle of Draetheus V. A Type-28 Spirit was also used by a Zealot to assist him in the terrorist attack on Sedra City. During the Battle of Installation 03 Jul 'Mdama's Covenant used T-28 Spirits against UNSC forces.
In Halo Wars, the Spirit only appears in the campaign and cannot be used in multiplayer or Skirmish. It is a fast dropship used to deliver large numbers of troops on the battlefield. Unlike Halo: Combat Evolved, the Spirit is not indestructible: it is advisable that players should eliminate it before the troops it carries disembark. Once the troops are on the ground, it cannot be destroyed.
The preferred units for taking down an airborne Spirit are M9 Wolverines, AV-14 Hornets, and AV-22 Sparrowhawks. Spirits in Halo Wars do not engage enemy targets and are only seen in the campaign, mainly on the mission Dome of Light and Repairs. Spirits in Halo Wars utilize gravity lifts to deploy and pick up troops, rather than the side-mounted troop bay doors as in Halo: Combat Evolved and Halo: Reach.
List of appearances