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The X303 Aegis is a commander-type mobile suit with very advanced sensors and heavy attack power. It can transform into a mobile armor configuration armed with a multi-phase beam cannon (which is later mounted on the GAT-X131 Calamity Gundam). For close-range combat, Aegis is equipped with 4 beam sabers. As these weapons are mounted on the forearms and feet rather than hand-carried, all four can be wielded simultaneously, in either mobile suit or mobile armor configuration.
The Aegis Gundam is transported to Earth shortly after the Battle of Orbit on February 13 to pursue Archangel, it is held at the Carpentaria Base in Australia until the Archangel passes through the Indian Ocean, where it is sent to rendezvous with the Vosgulov-class submarine Cousteau. The Aegis, Duel, Buster and Blitz Gundams successfully intercept Archangel in midocean and force the heavily damaged assault ship to lay over at Orb for repairs.
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We last see the Aegis Gundam as fragments of a destroyed mobile suit on the island where Athrun and Kira fought, the remains of this fallen metal giant finding their final, peaceful use as a playground for young children. Its shield was later found, if one looks carefully, at the black market auction for junk where Lowe Guele picked up the TMF/TR-2 BuCUE Tactical Reconnaissance Type head he used temporarily for his MBF-P02 Gundam Astray Red Frame. A variation on its transforming system is used by ZAFT, on a much larger scale, in the ZGMF-X11A Regenerate Gundam.
In Cosmic Era 74, the Eurasian Federation fields an upgraded version of the Aegis, the GAT-X303AA Rosso Aegis. The "AA" stands for "Advanced Acceleration". Piloted by Emilio Broderick, a pilot with Phantom Pain, the Rosso Aegis is very similar to the original, in that it retains the same three modes of transformation and has nearly identical armament. However, it has two very significant advantages: Unlike the original, it can fire its devastating "Scylla" multiphase beam cannon while in either Mobile Armor Attack Mode or in a "Mobile Suit Attack Mode" in which the torso component, which covers the barrel, is removed. And it can control the trajectory of the beam, much like the GAT-X252 Forbidden Gundam, but to a somewhat greater degree. Dispatched against the Martian Turn-Delta Gundam, it and the GAT-X207SR Nero Blitz were defeating their opponent, until repreated provocation by Turn-Delta pilot Ergnes Brahe caused Emilio to go berserk.
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Manufacturer: Morgenroete, Inc/Earth Alliance
Users: Earth Alliance, Zodiac Alliance of Freedom Treaty
Unit type: prototype commander use transformable mobile suit
Head height: 18.86 meters
Base weight: 79.9 metric tons
Special equipment: Phase Shift armor
Powerplant: Ultracompact battery, sustainable delivery approx. 2-3 megawatts
Armament: "Igelstellung" 75mm multi-barrel CIWS x2, beam saber x4, 60mm beam rifle x1, "Scylla" 580mm multi-phase beam cannon
Pilot: Athrun Zala