The Holy Empire Of Terra

The Holy Empire Of Terra is a highly fanatic empire setup in the southern fringes of the galaxy. Their goal is to take back Holy Terra and to purge the alien, the mutant, and the heretic.

Origins
In 2063 about a thousand people with hurtful opinions were exiled to the southern fringes of the solar system landing in a sector later to be known as "The Korplulu Sector". Everything was fine in the sector as the colonists had made a nice confederacy, an army made of loyal men armed with laser rifles, a capital home world named after the old american confederacy capital "New Virginia", and named their new interplanetary confederacy "The Terran Confederacy". But in 2070 their small confederacy and capital was seiged by bug like aliens. Though the aliens were defeated the home world was destroyed and government was collapsed causing the people to resort to anarchy. A year later in 2071 a tall godlike man in gold armor arrives on the planet. The godlike being calling himself "the god emperor of mankind" sets up an empire led by him and his 12 genetically modified sons later renaming the the capital planet from "New Virginia" to "The Grand Kingdom". Soon enough the empire has made a super soldier branch made out of power armor wearing soldiers implanted with the genetic material of one of the 12 sons. Sadly in 2100 half of the emperors sons and grandsons had betrayed him as they were worshipping void gods. 2102 the war end with the loyal team winning but the emperor getting mortally wounded in the final battle and having to stay on life support for all eternity.

Main Military Groups

 * The Imperial Guard is the main fighting force for the empire that has different aesthetics and styles depending on planet (example: one soldier from one planet may be good at horseback combat while another soldier from another planet may be good at trench warfare). The imperial guard is are the ones sent in to fight aliens or heretical beasts of the void. The imperial guard usually uses the idea of "one may fall but ten will take its place" when it comes to fighting the massive hordes of eldritch monsters as one may die but if you do enough bayonet charges at the demon you will eventually kill the beast. The weapons the Imperial Guard usually use are laser weapons with bayonets, ballistic weapons like assault rifles or pistols, and other weapons depending on specializations of the squad. Recruitment depends on the regiment as one may use cloning to replenish missing soldiers while another one recruits soldiers at birth and etc. The uniforms worn by the troops often change depending on regiment but the most common uniform is camouflaged fatigues, green pieces of armor and a green helmet with gasmask and googles.
 * Space Marines are the emperor's powerhouse. They are 8ft tall, wear power armor, over powered, and have lobster level immortality (age slowly but can die). They are usually deployed when the imperial guard need help because the bayonet charge idea didn't work. They are often born from dangerous planets and picked up at a young age to be genetically modified with augments from your specific space marine chapter to be strong and to survive in dangerous environments. They are all Male because the augments only work with males. The space marines are equipped with the holiest of weapons "The IM-32" also known as "The Bolter" it is a mix between an assault rifle and a grenade launcher as it fires soda can sized bullets at an enemy and explodes on impact, The more higher ranked or melee specified marines carry around blessed swords, space marines can also carry around flamethrowers for the purpose of burning heretics, and much more. Space Marines have different chapters that have different battle tactics and power armor colors.
 * The Cult Mechanicus are the people that make the empires technology, ships and weapons they are also the reason why the empire is in a technology stagnation. The cult mechanicus was discovered during the time when the emperor was retaking the former Confederate planets as when the emperor and his sons made land fall on one of the planets he found that the people on the planet had started worshiping the machine god and the emperor had started a pact with the mechanicus that they could keep their religion and culture of they join the empire and used their intelligence in technology into making weapons and technology for his empire and they agreed. The problem about the cult mechanicus is that they believe in a thing called "machine spirits" which is the belief that machines hold spirits that make them work. With that believe they think that alien technology holds "enslaved machine spirits" meaning that they have to free the machine spirit by destroying the valuable technology they could of studied and used for their benefits.
 * The Inquisition is the emperors secret police. They are separated into 3 groups: the ordo hereticus (deals with heretical civilians and void worshippers), the ordo xenos (deals with aliens) and the ordo daemous (deals with void demons). The inquisition are one of the highest authorities due to taking orders "from the emperor" so going against the inquisition will get you killed. The inquisition have their own personal armies: the grey knights a secret chapter of psychic marines that are sent to kill void demons, the sisters of battle are nuns with guns and like burning heretics, and the deathwatch which is an entire army combined of different space marine chapters.

Imperial Faith
The empire worships the emperor as a God and that the god emperor is all powerful and watching over you and helping you kill aliens and if you do not go to the imperial church then you are deemed a heretic you shall be executed infront of everyone.

Trivia
I stole most of this from warhammer 40k... sorry