Asteroidea merozoite

Asteroidea was the name given to a series of compounds developed by the Office of Naval Intelligence aboard the research and development station, Argent Moon. The compounds were designed with the goal of creating a biological weaponry that could remain dormant and asymptomatic as it spread through a population before being activated by a certain otherwise harmless aerosol dispersal. The formulas developed by the researchers were tested on live Kig-Yar prisoners, and possibly on unknown, misshapen creatures that were present in at least one laboratory on the station.

History
In March of 2558, an accident caused a particularly aggressive form of Asteroidea to vaporize and spread throughout the station via its air systems, killing nearly all aboard. Those closer to the accident were killed instantly, being liquidized from the inside out, and, depending on distance from the accident, the rest of the vessel's personnel began suffering symptoms from the chemical minutes to hours later. Although shipboard smart AI Rooker attempted to enforce quarantine protocols, they failed massively and all personnel aboard Argent Moon were dead by March 19. Two days later, Rooker made the decision to quarantine the vessel by jettisoning what portion of the Asteroidea compounds and dead bodies he could into empty space and setting the Argent Moon on a course that would keep it clear of any inhabited systems. He also recorded a message which was set to repeat for any potential ONI personnel that would try to reclaim the station, warning them that her air was not safe for humans to breathe. Rooker eventually succumbed to rampancy and chose to initiate his own final dispensation of September 12, 2557.

In October 2558, nineteen months after it went missing, Argent Moon was discovered by Kig-Yar scavengers, who sold it to Jul 'Mdama's Covenant. One week later, Spartan-II Blue Team was tasked with securing the vessel and its intel, encountering Covenant scavengers aboard the vessel. Unable to secure the Argent Moon, Blue Team was forced to overheat the station's reactor, destroying it and all of the remaining Asteroidea compounds aboard. Due to the station's obscurity, UNSC investigators who examined the remains of Argent Moon were initially unaware of the station's role, but upon searching the debris for clues, the investigators eventually discovered that the station's crew had been manufacturing a bioweapon.

Known compounds
Asteroidea 59B Subjects exposed to Asteroidea 59B sickened, but all recovered, with no fatalities. It was determined that the formula needed to be adjusted to increase toxicity.

Asteroidea 61F Morbidity in subjects was deemed satisfactory, but the LD50, or the dose that will be lethal to 50% of the targeted population, was not deemed inefficient.

Asteroidea 472A Both the morbidity and the LD50 were judged to be sufficient, but the shortening of the compound's half-life became the next goal.

Trivia
Asteroidea is the name of the biological class to which starfish belong. It is derived from the Greek aster, ἀστήρ (a star) and the Greek eidos, εἶδος (form, likeness, appearance).

List of appearances

 * Halo 5: Guardians