The Swarm

The Swarm was a vicious extragalactic insectoid species that invaded the galaxy in 2733. The subsequent war cost the lives of over 300 trillion Humans, Sangheilli and Therans and destroyed or devastated over 20 million worlds of the Unified Coalition of Governments.

History
The Swarm are speculated to have invaded the galaxy once before, long after the time of the Forerunners. Based on unsubstantiated evidence provided by an unidentified source on Thera, which may or may not be a Forerunner AI, the Swarm invaded the world of Thera. According to the source, it defended the world, along with the Therans, who were technically descended from Forerunners, with 'fire and vengeance'. It is not known if this event was related to the Ancient War, an apocalyptic event before the de facto founding of The Allegiance. The only evidence for it was carvings in ancient temples and archaic writings in obscure, long-dead languages.

The first confirmed contact with The Swarm was in 2614, when they invaded and massacred the small Allegiance scientific research outpost of Radiance. Due to the infrequent nature of communications between the outpost and the rest of the Allegiance, its destruction was not known until 9 months later. After this event they vanished off the galactic radar for more than a hundred years, before reappearing in 2733, triggering the galaxy's most massive, bloody and costly war since the Forerunner-Flood conflict.

Physiology
Although it was first thought that the Swarm was a collective of multiple species, it was theorised that the Swarm was of a shared genus with several subspecies or variations from what was otherwise a shared genetic code. This was supported by the fact that each of the Swarm types shared integral characteristics such as a tough exoskeleton and major internal systems, and shared large quantities of DNA with only a few major variations. It was theorised that these variations were not natural in origin but influenced and enacted by some unknown higher being/beings, though this remained totally unfounded.

The Swarm differ greatly between types, in size and many other areas. However, they all shared the same exoskeleton, formed of naturally occurring carbon nanofibre. They all maintained a core body temperature of 26°C, and shared their internal structure with little changes other than size.

Swarm Types
Despite the fact that The Swarm was one single species, there were several different 'forms'.

Drones
Drones were the most simple and most numerous of the Swarm forms. They were more intelligent than the other forms, possessing knowledge and learning skills just like a human or Theran would. Their average height was around 2m, though they could grow as large as 250cm before the end of their lifespans. They were stronger than the average human and possessed extraordinary endurance and resilience. Their faces were insectoid and their shape human-like. They possessed enough dexterity to wield most weapons in battle and could hold their own during combat situations. They were born already 6 feet tall and ready to fight, and continued to grow until the end of their lifespans which generally lasted about 20 years. They possessed tough exoskeletons which acted as natural armour to a certain degree, though it generally protected less from blades and as a result bladed weapons were popular throughout the war. Drones had to shed their exoskeletons every three to four years as they outgrew them. In actual fact, Drones were the adult form of Clackers, from which they transformed into after about two years. The older a Drone was, the more powerful it was and the higher it ranked in terms of military, with the oldest commanding vehicle formations or large numbers of infantry, similar to field commanders. Unlike some other Swarm forms, they had no larval and adult stages, instead lived their entire lives as Drones.

Reapers
Reapers were quadrupedal wolf-like organisms which the Swarm utilised in a rapid attack and melee role akin to shock troops. They were extremely fast, resilient and terror-inflicting, quickly decimating large numbers of infantry. They stood at an average of 190cm tall and were 260cm in length, and featured large razor sharp spines on their backs, and jaws that could crush a soldier's battle armour. They could commonly be seen charging directly at infantry or light vehicles at ferocious speeds, a powerful psychological weapon against enemies. They were sometimes used as stealth units, as their speed and hunter-like skills, not to mention their silence, meant they could easily infiltrate enemy territory and wreak havoc. While their use against infantry was famed and successful, they were rarely effective against armoured vehicles. Reapers were the adult form of Clackers.

Harpies
Often used as basic fodder units alongside the Drone, Harpies were much stronger and more potent however they were not nearly as intelligent. They were used akin to air support, also as rapid melee units to quickly engage enemy forces. They could easily pick up a fully armoured soldier and carry them to their deaths or feast on them on the wing. In large swarms they even posed threat to armoured vehicles and serious danger to less maneuverable air support vehicles, a notable example being the AV-14 Hornet. Armed with extremely powerful wings and razor-sharp blade-like legs, the sight of Harpies on the horizon often heralded the end for ill-equipped infantry. They were, however, quite weak against anti-air batteries, SAMs and more rapid air vehicles. Harpies were the larval form of Dragons, however not all of them transformed into them, with about 20% staying as Harpies and growing to large sizes.

Constrictors
A powerful Swarm type, the Constrictors were widespread and deadly, often used as war mounts and heavy infantry against almost anything on the battlefield. They were highly feared as a rapid threat able to engage infantry formations or armoured units equally effectively.

Tarantulas
Swarm Tarantula's were the largest known of the Swarm beasts, and fought on all fronts except space warfare. Huge, lumbering multipeds, they were naturally armoured enough to resist all but concentrated heavy weapons fire. Tarantulas were similar to Covenant Scarabs in most respects, used in the same manner as a heavy all terrain weapons platform for engaging any threats.

Clackers
Clackers were small and agile insect-like creatures, about the size of a child and acting in a ground support role for Drones. With vicious claws and dreadful bite, Clackers were so named for the chomping noise of their pincers and the horrible crunch made when they engaged their enemies. The lowest, most basic and most common form of the Swarm, Clackers were the larval form of Harpies, Reapers and Drones, which they transformed into after about 2 years of life. The mechanism by which an individual's adult form was determined remains a mystery.

Starships

 * Swarm Carrier-
 * Swarm Destroyer-
 * Swarm Hive Ship-
 * Swarm Cruiser-
 * Swarm Frigate-