UNSC Planet

Athenia Is the home of a humanoid race known as the Athenians (not to be confused with the Greek Athenians).
History:
The first recorded Athenians appeared after the Forerunners activated the Halo Array. At first, the Athenians all lived in a monumental city only known as Ethos. This city was built around a massive Forerunner installation known to the locals as "Zenith" The massive installation contained numerous floors, and in its very bottom sub level, a dormant gravemind known to the locals as "the tentacled god". Each floor contained forerunner machines ranging from destructive, to helpful. At the top floor, a massive beam that, when connected to the moon (which only lapses once every 1000 earth years), reverts all the inhabitants in a 10 mile radius (coincidentally the size of Ethos) into a more neanderthalic state(Meant to keep the gravemind dormant for another 1000 years). Most of the population saw this coming and decided to leave for new lands, while other parts of the populas saw this as great an stayed. When the pilgrims left for new land, the ones that stayed entered the zenith and got split up. 60% of the remaining population at Ethos ended up in the bowels of the Zenith and found themselves mutating into flood, at the control of the gravemind, they stayed and waited for actual orders. The remaining people found a sort of bunker floor, and waited until it was safe to come out.
After the forerunner beam hit the Zenith, the city of Ethos was destroyed and the gravemind and the infected citizens all went dormant waiting until the time was right to strike.
The pilgrims finally found the land and started to rebuild there civilization, and they developed a sort of democracy in their city-states. 
(2560)
The UNSC later found this planet after finding the radiation from a recent moon beam, and decided to investigate. Fascinated, they investigated the moon first, and found a sort of "kill switch for the beam". Not knowing what it did, they pressed it. seconds later the security system for the forerunner installation shut down, and released a contingent of flood. The Gravemind, now finding the neural signatures of his lost troops, commanded them to attack and infect the ones who activated the security override. The UNSC soldiers were slaughtered and infected, assimilating with the flood, and now under the gravemind's control. The flood searched through the facility for the ship that the humans came on (a colony class ship "Titus" carrying thousands of civilians). The flood came out of the facility and met face to face with a UNSC War hound (A sort of zero G scorpion armed with a napalm cannon. While that stopped a small part of the force, spores quickly seeped through the canopy of the War Hounds, and the drivers were soon infected. Seeing the bio-signs of his troops go dead, the colony class ship's captain and the remaining 1000 marines and ODST's, decided to pull out and land on Athenia. 
When the UNSC landed, they quickly deployed a base and kept the Colony ship in orbit. After establishing a base, they found out that the locals were actually winning against the flood and that they need extra men to push into the Zenith and stop the gravemind. The Athenians and the UNSC allied and launched a large scale attack on the Zenith. After a large battle, and with both sides losing numerous forces, a contingent of Athenians, marines, and scorpions stormed the gravemind's chamber. After finally destroying the gravemind, the UNSC and Athenians allied together.