Before all else, it is crucial to understand that the very name 'Empire on Thyrsus' is something of a misnomer. While this appellation for the break-away Imperial state centering on the Thyrsian Sector was utilized widely by it's contemporaries and historians, we have no indication that Cyrian Arkanius or any of his followers ever referred to themselves as such. Indeed, all official transmissions and decrees that we have available to us were transmitted under the authority of the Galactic Empire, with Cyrian as it's Galactic Emperor. There is no indication that the notion of a literal Thyrsian Empire was ever entertained seriously by anyone beyond fringe sects of the Sun Guard fighting for Cyrian Arkanius, despite frequent propaganda attempts to frame it otherwise. Competing realms such as the Core Region under Grand Vizier Mas Amedda, the Divine Empire, Warlord Zsinj's military potentate and other numerous splinter states were viewed as illegitimate usurpers.
A popular point of contention is to what degree, if at all, was Cyrian's Empire a theocracy along the lines of the Pius Dea worshiping Divine Empire. Legally, the Empire on Thyrsus was entirely areligious. Cyrian Arkanius' claim to the throne of Galactic Emperor was based on the alleged will of Emperor Palpatine as dictated by the Imperial Guard. Ostensibly, there was no requirement to hold or convert to the Thyrsian Twisuns faith and many non-Thyrsian Imperial units such as the majority of Cyrian's naval assets and much of the remaining Imperial-Royal Guard, without religious motivation. The reality of the situation, however, was deeply muddled.
The famed Sun Guard, reformed and reinstated as Imperial Legions, compromised the mainstay of Cyrian's forces. Not only did these warrior-fanatics represent an absolute majority of Cyrian's military force in numbers, but also individually had the value of a standard Imperial soldier or even Stormtrooper easily a dozen times over. These men who possessed the skill, tenacity and raw ferocity (or perhaps madness) to contest even the Mandalorians innumerable times would be the linchpin of any hope to claim the Imperial Center. In order to effectively hem in these insatiable fighters, Cyrian appealed to their faith: He fashioned himself as the Per Kharshad, or mythological Son of Suns - the prophesied messiah of the Thyrsian race with the backing of the Sun Priests. It is debated whether or not the Thyrsian Priesthood was coerced into doing so, though the interpretation I hold is that the Priesthood recognized Cyrian as a potential avenue in spreading their faith across the Galaxy. Keenly aware that the Sun Guards could never follow someone perceived as a weakling, Cyrian also frequently fought along side their ranks, putting his skills as a Imperial Sovereign Protector and former Sun Guard himself to devastating use.
Essentially, it can be summed as such: while Cyrian Arkanius fashioned himself as Galactic Emperor on a secular basis, the most potent of his manpower followed him with religious motivations, mixed in with nationalism - the Sun Guard could hardly be opposed to the notion of a Thyrsian Emperor - and hopes of enrichment and thus had to be appealed to on such lines. Imperial Navy and Stormtrooper units frequently complained of coerced proselytizing attempts and witnessing forced conversions by members of the Sun Guards on captured civilian and military units along with illegal executions via prolonged exposure to the elements referred to by the Sun Guard as 'Judgment of the Sun.' The appending of a sun to the typical Imperial emblem succinctly represents the appeals to the Sun Guard and clout they wielded in Cyrian's Imperial government.
The Sun Guard's History
The Sun Guard hail from the planet Thyrsus, a sun-baked and intensely hostile world consisting mostly of sand and dry savanna inhabited by all manner of dangerous wildfire. Thyrsus was originally a colony of Eshan, homeworld of the Echani. Over long years, the Echani colonies diverged not only physically from their progenitor species but spiritually as well. The Twin Suns of the planet came to be seen as a harsh, merciless but ultimately benevolent extensions of a deity that could both melt away and nourish life. The Thyrsians came to resent the Echani who were viewed as heathen overlords, made soft by easy living and over-reliance on the guidance of their females. When the Thyrsian Special Forces sub-command of the Echani Military was ordered to suppress the Bengali Uprising, they revolted and instead joined Bengali against the Echani. These proto-Sun Guards waged a intense insurgency against the Echani for nearly two centuries in a conflict that waxed and waned between asymmetrical fighting and conventional warfare until independence was achieved with the Pact of Almera.
Faced with a blood-lust not yet sated, a desolate and inhospitable home-world and an entire generation of men and women who knew naught but war, the newly independent Thyrsus embarked on campaigns of raiding and expansion. Slaves worked and nourished crops irrigated in the underground while the Thyrsians themselves lived in sprawling cities around sand oases. Eventually the most elite of these warriors organized themselves into the Sun Guard. The Sun Guard would gradually progress from the elite warrior caste of Thyrsus, to it's rulers and finally semi-nomadic warriors that served as mercenaries once Thyrsus was subdued by the Republic, in a similar manner to their rival the Mandalorians.
The Sun Guard was eventually seduced by the Sith, who presented themselves as the subjects of their Per Kharshad prophecy and promised them power and splendor in the Galaxy. The Sun Guard would be formally disbanded under Palpatine, with many of it's units joining various Imperial military organizations with the Imperial-Royal Guard the foremost among them. Cyrian Arkanius later reformed the Sun Guard from Thyrsian warriors, renegades and successor organizations and designated them as the first of his Imperial Legions.
Culture and Military Operation
Thyrsus is a relentlessly brutal warrior-centric military society, the product of a relentlessly brutal planet and a relentlessly brutal, centuries-long independence war. Thyrsus is dominated by a number of Great Houses with Zardaukar and Scipius among the most famous of them, ostensibly united in a Sun Council but frequently at, often violent, odds with one another. Thyrsians are initially bestowed a given name and a House name when born, with the exact nature of the latter depending on whether they're born as apart of the Great House or merely in service to it - the influence of the Great Houses are as such Thyrsians are rarely born from parents not, at least formally, in service to one. If apart of the Great House, it's name is prefixed with 'Ri' and taken as their own. If only a servant, then 'Rishah' is the prefix. Through prominent military feats, a Thyrsian may earn a final, more prestigious personal last name usually based on the location or nature of the victory. For example, as a blood member of House Zardaukar, the Emperor was born as Cyrian Ri-Zardaukar. With his holding action on Arkania, he became known as Cyrian Ri-Zardaukar Arkanius or simply, Cyrian Arkanius.
In their hey-day, virtually every single Thyrsian was either a full-time warrior or a retired one, relying on slaves and basic automation - Thyrsians have for a distaste for droids and A.I, who they disparagingly refer to as 'thinking machines' - to do the mundane work of agriculture and industry while devoting themselves entirely to conducting warfare. Under the Republic and Empire, campaigns of expansion were ceased and raids lessened, but not entirely eliminated by no means, to the extent where the majority of Thyrsians practice a sort of yeoman-warrior sort of living. A moisture farmer family, honed by combat against vicious wildlife, the Echani inherited combat-communication culture and skrimishes between Great Houses, may embark on an raid with the aspiration to supplement or perhaps even entirely replace their labor with slaves and dedicate themselves wholly to combat. Juvenile Thyrsians assist their fathers, mothers and older siblings in combat until they are old enough to fight effectively themselves, typically getting their first tastes for killing sentients at a very young age on elderly and sick slaves. While opposed to the matriarchal Echani, the Thyrsians are not usually considered outright misogynist, instead possessing the typical male-oriented view akin to humans and other similar species.
Young Thyrsians who wish to prove themselves undisputably as warriors, embark on a quest to hunt down and kill the massive Gebi Sandworms and extract their endocrine glands in what is known as the Raad Andraf - Ritual of Making. This is typically done in groups due to the danger and the fact that each worm carries enough glands for multiple men, but the most bold of Thyrsians do so alone. Sometimes Thyrsian Cave Hawk Wasps are hunted as well, and their venom utilized to make tattoos. Once home, the endocrine glands are implanted by Sun Priests to complete the Raad Andraf. These glands passively excrete hormones that increase the Thyrsians combat performance, but may be consciously or unconsciously triggered which flood the Thyrsian with potent Gebi adrenaline and hormones that send them into a nearly unstoppable frenzy. The Sun Guard require the Raad Andraf to be completed as a barrier to entry, and any Thyrsian who successfully undergoes the process have a good, but not guaranteed, chance of gaining their interest. Thus every Sun Guard possesses the Sandworm glands, but not every Thyrsian who possesses the glands are apart of the Sun Guard.
In terms of weapons, the Sun Guard utilize a vast variety of blasters and other such weapons, but are renown for a few pieces of equipment.
Sun Guard Armor - The infamous Sun Guard helmet was originally a visor made by the proto-Thyrsian colonists to keep the sun of their eyes while working. Sun Guard armor, while often crafted to a high quality out of various materials such as durasteel or even phrik, depending on the Sun Guard's particular station and success, has no unique qualities such as the Mandalorian beskar'gam besides being extremely well heat-proofed due to the Sun Guard's fondness for flamethrowers and other heat-based weapons.
Thyrsian Flamethrowers - Devised originally to clear Hawk Wasps from their caves, various forms of Flamethrowers are a weapon of choice for Thyrsians and by extension, the Sun Guard. There is a religious significance, for the Sun Guard believe that fire contains the essence of the Twisuns, and thus there is almost an grim mercy in putting foes to the flames, for they are becoming closer to the true faith as they are cleansed. Thyrsian Flamethrowers utilize Gebi Sandworm bile, which burns with such a vigor that the flames burn almost as easily ontop of and even in water as they would open air and need to be nearly entirely deprived of oxygen to snuff out. Due to the obvious problems with mass production, a slightly less effective synthesized version of Sandworm is widely utilized.
Kypesh (Thyrsian Sword) - Along with force pikes and other melee weapons, the Kypesh is a popular melee weapon favored especially among the Sun Guard. It is a straight, tapered vibrosword, excellent for thrusting. Like all vibroswords, the Kypesh is based off of Echani designs, differing from most vibroweapons with a much larger and accordingly more powerful energy cell. The oversized energy cell makes it a finicky weapon, the constant competent maintenance required suited towards professional soldiers such as the Sun Guard. When activated, the excess heat is channeled directly into the specially treated blade and, combined with the additional friction from the vibration, results in a weapon that frequently glows orange or red and can combust objects on contact. However, it is especially vulnerable to electric current, even for vibroweapons, resulting in Sun Guards usually being reluctant to activate the weapon when fighting against force users, especially Dark Jedi. In such scenarios, Sun Guards typically resort to their force pikes.
Phalanx Shield - The Sun Guard utilize a wrist mounted energy shield adapted from Echani technology. Once activated, the energy shield expands outwards, typically enough to cover the entire front of a man, but can be adjusted freely. What is unique about the Phalanx Shield is it's energy 'absorbent' properties, which are exploited by the Sun Guard in formation tactics. The Phalanx Shield can 'interlock' with other Phalanx Shields, combining their power into an extremely tough if albeit sluggish energy bubble. Whether interlocked or individual, Phalanx Shields utilize the same technology to enable itself to absorb energy from enemy blasters. Once sufficiently overloaded, the Phalanx Shield can unleash this energy in a blast. One common strategy utilized by the Sun Guard is to advance in interlocked Phalanx formation, absorbing enemy fire across a no man's land until close enough to unleash a massive wave of energy. The Sun Guard then charge into close combat with the reeling enemy, in which they excel, burning and chopping the enemy to pieces with the advantage of their glands and Echani-inherited battlesense.