Vixel

Vixel, also known as Serria-Sora IV, is a human colony in the Serria-Sora system within the mid-colonies. It lies around 42 light years away from Earth and it stands as the largest planet within the system.

The planet was used as a military powerhouse and industrial world as well. Unlike most colonies, Vixel was not invaded by the Covenant but was attacked by a Covenant Remnant group the Fleet of Regretful Redemption, led by Fin Krudom.

Colonization
Vixel was founded by human on May 23, 2353. Originally colonized during humanity's first wave of extrasolar colonization in Sanus, Vixel was first colonized due to its rich deposits of topaz, rubies and other high luxury items that could be sold. Large titanium deposits were also located within the modern day Republic of Gonan.

The moon of Vixel was nicknamed Starro and was also the site of a supply depot and drop off point, making the moon the largest area of trade on the planet.

The planet was also turned into a military powerhouse due to location and mines and thus a large UNSC presence was established in the three biggest cities of San Andreas, Mekron and New Century.

Insurrection
While it's years of colonization, a formal Insurrection movement wasn't formed on the planet until 2500, when rebels attacked a small army outpost, Cedarhill Base, in the nation of Patch.

As a response, the UNSC began countermeasures on the planet which resulted in a swift UNSC attack on a small rebel cell by original ORION Project members. The planet also suffered from a major bombing incident in 2522 on the Island Trio nations of Vale, Atlas and Vacuo.

Though UNSC response was swift, major population centers were hit and several died as a response to the Insurgent attacks. Luckily all attacks would cease with the begging of the Human-Covenant War in 2525.

Human-Covenant War
Though Vixel was never attacked by the Covenant during the war, it still supplied the UNSC with armament and vehicles during the efforts against the aliens. Such things included, , and. As such, the colony severed as a large UNSC power house during the war.

Battle of San Andreas
On June 18, 2558, the colony was attacked by the Covenant Remnant group The Fleet of Regretful Redemption. However, the fleet only targeted the city of San Andreas. UNSC response was strong but it still wasn't strong enough to halt the alien advance from entering the city. As a response, on June 22, the UNSC deployed the Alpha-Zulu Corps with Shield Team to stop the Covenant.

The remnant group made advances through the city until the UNSC launched a counterattack to clear the outskirts of the city in Little Rock outpost.