Ground Warfare

Ground warfare still uses ancient ground technology like projectile weapons tanks and projectile weapon artillery, aka conventional war. The types of stuff you would see on the battlefield are soldiers in advanced armor, Knights in exo-suit power armor, different types of tanks or ground vehicles, including artillery, and different kinds of flying ships, including the Eques-Class Steed/Fighter used in both interplanetary combat and space combat.

Air and Space Warfare

Space warfare is multifaceted, with many significant weapon systems used by the Empire's factions and nobility. Most warships used by poor counts, independent traders, and merchants are repurposed civilian craft. Still, those of the rank of Duke or higher often controlled their own forge worlds where they could produce custom military ships ranging from single-seat fighters to the mile-long Imperatoris Class Cruisers. Most HRE space-based military forces focus on chemically-propelled missiles of every size and type imaginable, from finger-sized radar-spoofing missiles to massive anti-fleet strategic thermobaric missiles. Laser-based weaponry is also used, ranging from the low-power Laz Class flares used to destroy missiles and debris to the extremely high-power Laz Class cannons built to wipe out mass driver projectiles and other large-scale attacks.

Magic or Void Mages

Void mages are powerful magic casters who use the magic of the void, each belonging to many different orders. Each order can only use one or two types of powers, but generally one. Some orders have members of both sexes, while others are purely one sex or the other. Void magic can create portals to travel across large swaths of space or a planet and slow or speed up time in a defined area/range for no more than a few seconds at a time. Manipulation of space and void mages could shape reality to a limited extent. They might create illusions, bend light around objects to make them invisible, or even alter the properties of matter within their immediate vicinity. They can also use telepathy to communicate with each other or with other beings telepathically, bypassing language barriers and facilitating covert communication. Powerful void mages can use void magic to create artifacts from the Red Magic Mist that can nullify all use of magic ranging from a small region to an entire planet and make artifacts like near endless energy.

Knights

Knights are some of the lowest-ranked nobility unless they hold a noble title. Although low-ranking nobility, they are the best fighters in the galaxy, especially those trained by the imperial trainers. They are trained to be excellent pilots flying the Eques Class Steed/fighter, which is a type of large fighter that can be used in space and inside of the atmosphere of the planet, as well as being trained in ground combat using exo-suits that increase the strength of the user threefold when in ground combat they use projectile weapons that are bigger than the weapons used by the typical soldier and more powerful, as well a vibro blades, roughly half the size of the user, to cut through shielded enemies, as the vibration of the vibro blades allow them to distort the shield allowing the killing of the target by cutting through the armor. The knights descend from humans that have been genetically enhanced to be faster, stronger, etc. than your average human this goes for all orders of knights, and these genetic enhancements are passed down to their children. 

Infantry

Most modern infantry of archdukes and below are armored with armor that can defect low caliber rounds from guns like projectile pistols. It looks very similar to old armor from the early 2000s in the empire's past. Soldiers in the Empire can often be found using projectile weaponry slightly more advanced than what was used eight thousand years ago.

The armies of Princes and the Emperor can field infantry with more advanced armor that deflects lower caliber projectile rifles when shot in the chest. However, it will only block several rounds before being penetrated. At the same time, they use projectile rifles that are more advanced than your average soldiers.