The Legiones Titanicus, or the Titan Legions as they're more commonly known to the innumerable masses of humanity, are the elite fighting forces of the Moritanian Star Empire. The ten Legions are exemplars of the human fighting spirit, embodying the highest ideal of service to the Empress. Each Legion is the equivalent of an entire army of MSE Marines in firepower.

The history of the Titan Legions dates back to the middle of the 23rd Century. A mere ten years before the outbreak of the Terran Alliance Civil War, it was decided that a force of superhuman warriors would be established to augment the Terran Alliance Marines and Stormtrooper Corps. Work was begun in secret on what would become the First Legion, the Swords of Latium. The initial recruits for the Legion were drawn from the best soldiers the project heads could find from both the Marines and the Stormtroopers, in order to meet the set quota of one hundred thousand.

Ten years into Project Titan, the Civil War broke out. With only 33,624 of the projected two hundred thousand Titans complete in their augmentation and training process, the Alliance High Command ordered that the Legion be deployed in a series of covert missions to test their battle-readiness. This meant that the Legion was away from Earth when the Separatists struck in 2263. For five years, the Swords of Latium campaigned against the rearmost elements of the Separatists, while their main fleets dueled the Loyalists at Earth.

It was not until 2268 that the Swords managed to return to Earth, having seriously destabilized Separatist resistance and supply lines from their core worlds. The Legion smashed through the surviving Separatists, and then spent the next year helping the remainder of the Army, Marines, and Stormtroopers clear the Seppies from the Sol System. The Swords then embarked, alongside the Stormtroopers and Navy, on a campaign to strike hard at the now-beheaded Separatists and purge them from the galaxy.

For the next seven hundred and thirty years, the Swords of Latium expanded to their modern size of 200,000 Titans, helping the GUDF Marine Corps, Navy, and Starfighter Corps police and protect the Galactic Union of Humankind which rose in 2273 as a result of the Civil War. The next major action the Swords were involved in was the First Reptoid War of 3010-3013, which resulted in a minor victory for the GUoH. It was twenty years after the end of the FRW, 3033, that the Senate recognized that another Legion of Titans was needed to help police the ever-growing Human empire. Thus was born the Second Legion, the Gallic Templars.

Through hundreds of campaigns across the centuries, the Swords and Gallic Templars were joined by other Legions, the III 'Eyes of Aquarius', the IV 'Spears of Hokkaido', the V 'Sagittarians', the VI 'Huang He Tigers', the VII 'Librans', the VIII 'Adamant Angels', the IX 'Perseians', and the X 'Capricornians'. At present, there are approximately two million Titans serving in the entirety of the Legions, with ranking officers devoted solely to command of the Legionary fleets.

The pride of any Legion's fleet is the battleship, an eight-mile-long warship capable of outgunning a pair of MSE Navy Dauntless Dreadnaughts. Due to the fact that there's only one battleship per Legion, it is always that Legion's flagship and is under the direct command of the Legion's Admiral. Notable examples of battleships include the Gloriam Terranus of the Swords of Latium and the Pride of Alesia of the Gallic Templars. Other ships of the Legionary fleets include medium cruisers, assault cruisers, strike destroyers, and strike frigates.

As for the organization of the Legions themselves, each Legion is led by an officer called a Legate. Legates invariably have centuries of battlefield experience and have earned their rank by fighting in hundreds, if not thousands, of battles during their lifetimes. The only way for a Titan to attain the rank of Legate is to have been the First Colonel of his or her Legion. There has never been a female Legate in the history of the Legions, however. The Legate is personally promoted to his rank by the Council of Legates, a body consisting of all ten Legion commanders. It is they who dictate policy for the Legions and answer to the Senate. The Legates are directly senior to the Legionary Colonels, the officers who command each of a Legion’s ten Regiments. Regiments consist of 20,000 troopers each, and are divided into forty 500-man companies, commanded by Captains. Each Regiment’s First Company consists of the Devastator-armored elite, led by the Devastator Captain. The Devastator Captain of the First Regiment of each Legion is also known as the Devastator Knight Commander. Captains are advised by their company’s Senior Sergeant, who also serves as the leader of the company’s First Squad. The Captain and Senior Sergeant of each company oversee the Sergeants of the company’s other squads, as well as company vehicles and other resources. Each sergeant oversees nine troopers, individuals who have for the most part just risen up from the ranks of initiates, some of them older and more experienced than the others.

Recruits for the Legions are drawn from a number of sources in the 13th Millennium: Most recruits come from the Marines, specifically those troopers who have proven themselves with acts of singular daring and bravery. On occasion, the Legions will descend upon their homeworlds and take the best and brightest children for training, but generally this practice is frowned upon by the galaxy at large.

The Titans are armored in the renowned X-42 Variant Omega Powered Assault System, an evolution of the Variant Alpha used during the Civil War of the 23rd Century. The elite Devastator Companies use the Devastator-class Variant Omega, which sacrifices mobility for increased protection and firepower. Devastators are not as fast and agile as their brethren in the standard Variant Omegas, but are more lethal in ranged combat and close-quarters battle.

Vehicles used by the Legions include the Manticore battle tank and the Redtail gunship.