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This article is about the Halo: Fireteam Raven level. For other uses of “Alpha Base”, see Alpha Base (disambiguation).
Having returned from the raid on the downed Pillar of Autumn nearly sixty hours after landfall, Fireteam Raven are briefed on the ring by Wellsley. Mid-briefing, Alpha Base comes under attack for the second time, and Fireteam Raven assist in its defense. Before the battle is finished, however, Raven are recalled to deal with an emerging threat elsewhere.
The camera shows the mesa hosting the UNSC's Alpha Base, before switching to inside one of the tents. Fireteam Raven and Major Silva are gathered around a holotable showing Wellsley's avatar, while Falcons, marines and Warthogs can be seen in the background.
Wellsley is cut off as an explosion rocks the base. The camera then cuts to a sweeping shot of the base, as Dextro Xur-pattern Spirits are shown beginning to land around the base, while the defending troops fire back. A Falcon takes off from the base's landing pad as Banshees begin to conduct airstrikes.
The camera switches to first person view, as Raven equip their MA5B assault rifles and M9 fragmentation grenades. They exit the tent in time to see two marines killed in an explosion, and round a corner to see a trio of Spirit dropships flying overhead.
Raven begin firing upon the assailing Banshees with their rifles. Four craft are destroyed, before several Sangheili enter the battle on the ground. In the background, a Spirit lands on the base's landing pad and deploys its troops. The Elites are reinforced by Unggoy and Yanme'e. Fireteam Raven turn around to see another lance of Sangheili and Kig-Yar led by a Sangheili Major wielding an energy sword. The infantry are killed moments before a Warthog drives through the battlefield. In the distance, one of the base's M910 Rampart guns, scavenged from the Pillar of Autumn, can be seen firing.
Fireteam Raven round a corner to find another Spirit dropping its troops into the courtyard, this time led by an Ultra Sangheili. The players are joined by some marines, who are quickly killed by Banshee air strikes. The players look up to see a Pelican, hit by the strike, fall to the ground and explode.
The marines and Raven are set upon by a squad of Grunts, who are reinforced by several Major Sangheili. A Phantom dropship then enters the mix. The players pick up an M41 SPNKR leaning against a barrier, which they use to fire upon the craft and destroy it. Raven then turn around to see several Ghosts entering the base, which they use the rocket launchers against. Raven then switch back to their plasma rifles to engage several Jackals and drones. As the squad nears the Shades, they are engaged by some more Elites Grunts and Jackals. The squad is joined by two marines.
A Spirit dropship appears above the players, opening its doors to reveal a pair of Hunters. The two swat away the Marines and engage Fireteam Raven, but are soon killed. The squad then mount the defensive Type-26 Shade turrets, and begin firing upon the encroaching Banshees and Phantoms, supported by Pelicans. Several waves of Covenant aircraft are repelled before a new threat emerges; a Kmiro'sish-pattern Lich, the Upright Chalice, descends from above and levels over the base. The players are able to fire inside the Lich and its infantry payload within before the craft departs. The Lich then turns around to reveal the other side of the troop bay and more infantry, this time led by a Sangheili Zealot. The Lich flies away from the battle, leaving only one final wave of Banshees before the squad exits the turrets.
Fireteam Raven equip their assault rifles once again as they begin to make their way to the evac point. They encounter more infantry before two Phantoms drop off another pair of Hunters to deal with. A damaged Ghosts attempts to join the battle but crashes into a cliff, it's occupant dropping a Needler for the players to use. The squad engages more Sangheili on the cliff above them, before two Hunters move in behind them and engage. Overhead, a Falcon chases a Banshee past the squad as they begin to move into the main Forerunner structure comprising the base itself, engaging Unggoy and two sword-wielding Ultras. Two more Phantoms drop off yet more Hunters and some Suicide Unggoy. As the squad rounds a corner, a squad of Marines can be seen on the landing pad fending off several Jackals and Suicide grunts. The infantry dispatched, and a Falcon arrives to land on the landing pad.
The camera cuts to Fireteam Raven boarding the Falcon, with Marines protecting their rear. The Falcon lifts off, and the mission ends.