Decimus was a Jiralhanae warrior who founded the Banished alongside Atriox when the two of them and several other Jiralhanae rebelled against the Covenant Executioner. Decimus had been serving as Atriox's right hand and second in command ever since, and was a general in the Banished.
The Covenant and the Banished
Decimus once served in the Covenant's military. He fought in the genocidal war against humanity. He was present on Algolis when Atriox, the survivor of numerous suicide missions and a disbeliever in the Covenant's Great Journey and the war, was meant to be executed. He was inspired by Atriox's refusal to allow himself to be killed and his defiance of the giant empire. At that moment Decimus sprung into action. He and other Jiralhanae killed all of the Sangheili present in the immediate area. Decimus personally was responsible for numerous deaths, which he caused without the aid of any weapons. Forthwith, he fell to both knees before Atriox and pledged to follow him. From that day onward, he was Atriox's right hand. He served in the Banished as a general and had command of multiple types of units, including Jiralhanae Warlords and Unggoy thrall-taskmasters. He accompanied Atriox during raids on Covenant supply lines and stores to build up a formidable amount of ordnance stolen from the empire.
Recruiting Sig Raan
After the foundation of the Banished, Decimus travelled to a secret Covenant facility on the planet Otraak to attempt to recruit a Kig-Yar scientist named Sig Raan in an effort to expand the Banished's technological base and support their fleets.
Dealing with Jovus
In November of 2558, the Banished arrived in force at Installation 00 aboard the Enduring Conviction. Decimus personally led the subsequent attack on the humans at the Henry Lamb Research Outpost. He and a contingent of Banished ground forces massacred everyone in sight easily. Following this, Decimus was charged with establishing a system of power extraction and excavation across multiple sites on the Ark. In addition to plundering the massive Forerunner installation's resources, he also directed the collection of salvage left over from the prior battle in 2552. Over the next few months, these endeavors grew in scope. Accessing a Cartographer allowed the Banished to take control of the installation's local portal network, which made travel and coordination between many sites much more effective.
When the UNSC Spirit of Fire arrived at the Ark on March 28, 2559, one of the first things the Banished were required to defend was one of these sites where Decimus was in charge of resource gathering. Around R-6029-4452 according to a Sangheili method of keeping time, a base under the control of Decimus was destroyed by Jerome-092 and Strike One. At first, the Jiralhanae general was unaware as to why contact had been lost with his contacts at the base, but it wasn't long before the attack and the humans' presence became known to him. At first, he called for shipmaster Let 'Volir to target a newly-built UNSC firebase with pulse laser turrets as a short show of force. As the Marines and the Spartan weren't dissuaded, however, Decimus finally appeared on the battlefield himself. From the ground, Decimus not only took on the many fighters himself in close-quarters combat, but also repeatedly ordered the shipmaster to target his own location briefly and with precision as he was protected from the lasers by a powerful energy shield that his mechanized power armor could encapsulate him in for short periods. When it became clear that he would not be able to fend off the attack, Decimus retreated but the Enduring Conviction continued to bombard the area on his orders, killing UNSC and Banished troops alike, ostensibly to keep the humans from learning anything from the operation. He was ordered to report to Atriox immediately following this loss. Despite Decimus' best efforts, the humans were able to recover records from Decimus' base pointing them towards the Cartographer as their next target.
Decimus would not step into the fray again until two days later on March 30, when UNSC forces were making a push to cripple the portal network by destroying its central hub. He had been reassigned to protect the portals after the extent of the network was discovered by the enemy. Decimus, enraged, made a bold stand against the aggressors, wherein he coordinated with the Enduring Conviction similar to the previous engagement. The combined fire from many UNSC infantry, vehicles, and aircraft along with Spartans Jerome-092 and Douglas-042 heavily damaged Decimus and his exoskeleton. Mortally wounded from the immense firepower, Decimus collapsed to his knees and ordered the humans to enjoy their victory as it would be their last, before dying.
Personality and traits
Decimus was ruthless and extremely bloodthirsty, boasting almost unparalleled, raw physical strength. Fighting for the glory to kill, Decimus was considered to be the embodiment of every horror story that has been passed around through the UNSC Marine Corps about battling Jiralhanae. When he served the Covenant during the Human-Covenant War, he took particular delight in hand-to-hand combat with the outmatched soldiers of the United Nations Space Command. Decimus respected strength above all else and held the traditional Jiralhanae belief that "might makes right"; Atriox gained Decimus' absolute loyalty after he successfully rebelled against the Covenant, becoming known as his right hand. As befitting his rank, Decimus had his own personal Jiralhanae Warlord lieutenants but he also relished the chance to make a personal appearance on the field against particularly stubborn enemies. Decimus' bloodlust often whipped troops under his command into a frenzied rampage. While the Jiralhanae who make up Atriox's Chosen share their leader's cunning, Decimus encouraged more base traits in his warriors, chief among which was the unquenchable thirst for blood. Decimus showed little care for the troops under his care, ordering an orbital bombardment from the Enduring Conviction on his salvage base to cover up his operations while Decimus himself escaped through one of the Ark's portals. The bombardment killed many of his own troops disgusting Isabel who called Decimus a monster for his heartless actions.
Decimus still harbored resentment against the Sangheili that serve the Banished due to how they treated the Jiralhanae in the Covenant. As such, Decimus took a sadistic joy in ordering the Sangheili of the Banished on dangerous, and often suicidal, missions. Like Atriox, Decimus despises the Covenant and its remnants. Unlike many in the Banished, Decimus secretly continued to harbor a belief in the divinity of the Forerunners right up until his death. Orda Val 'Saham, a Sangheili guard who reported to him, noted that he regarded the Forerunner architecture on the Ark with reverence and awe. In his eyes, 'Saham saw what he regarded as a fatal longing and a tragic need to be struck dumb and blind by the promise of a wondrous destiny.
Decimus wore a powered exoskeleton into battle when the Spirit of Fire appeared at the Ark. This exoskeleton increased his strength and granted him a great deal of protection from weaponry. When engaging UNSC forces for the second time, Decimus bragged that his armor had been improved in the meantime since the last fight. Decimus wielded a modified gravity hammer that could be used to pull vehicles and infantry toward him so he could then smash them, in addition to unleashing a devastating gravity vortex.
List of appearances