Power Armour

Power Armour is a science fiction concept of armour which increase the strength, speed, and reflexes of those who wear it. It features heavily in science fiction/fantasy settings such as Warhammer 40,000

Space Marine Power Armour

The most iconic users of Power Armour in 40k are the Space Marines and the Chaos Space Marines. Made of ceramite which will deflect all but the most powerful of weapons, Power Armour possess many life support systems designed to keep the Space Marine inside alive. The Black Carapace, one of the Gene-Seed organs, is specially designed to interface with the Space Marine, and is the last organ implanted in Codex Chapters. Amongst its features, Power Armour possess auto-senses which enhance the Marines already considerable senses, injects pain killers in the event of lost limbs, and recycles the waste of the body into a nutrient paste which will keep the Marine going for up to fifty days without needing to eat again. The power source is a backpack mounted generator which needs initializing, but after that can take solar energy to keep itself going.

There are eight types or Marks of Power Armour used by the Astartes. Regardless of their type, they all have massive Pauldrons.

Mark I: Thunder Armour

The first type of Power Armour designed, these were used by many of the techno-barbarians of Terra. They provided the basic protection against weapons and enhancements of speed and strength, but that is all. Since they were used on Terra, Luna, and Mars at this point, there was no need to protect them against the void. Though the lack of life support systems make them essentially useless to the Space Marines in the 41st millennium, several Chapters retain sets of Thunder Armour for completions sake.

Mark II: Crusade Armour

Designed by the Adeptus Mechanicus with the Great Crusade in mind, the Mark II armour contained the life support systems and void sealed features so common amongst the Space Marines. The chest coils, which were external in the Mark I for cooling purposes, were now internal and better protected due to more efficient cooling systems.

Mark III: Iron Armour

Mark III armour was designed initially with the idea to provide better frontal protection during the campaigns on the Squat homeworlds (later changed to boarding actions). Mark III was slowly being phased out with the Terminator armour by the time of the Horus Heresy, but it's still fairly common among the Traitor Legions.

Mark IV: Imperial Maximus Suit

Now having access to more of the Standard Template Constructs, the Mechanicum was able to further refine the Power Armour's systems. In addition to more enhanced vision spectrums, the Space Marine could now turn their head in the Armour. As the Legions were either fully or partially equipped by the time the Horus Heresy began, Mark IV is one of the most prevalent types of armour among the Chaos Space Marines.

Mark V: Heresy Armour

In between production of the Mark IV and what would be the Mark VI, the Legions found that they were running out of replacement parts for damaged systems. This would result in several Legions taking parts from older Marks and inadvertently making a brand new Mark of Power Armour. Although its appearances varied widely, some form of standardization was achieved. One of the most notable was the introduction of molecular bonding studs on the left pauldron.

Mark VI: Corvus Armour

The much beloved Beakie armour. Although it featured no improved protection, Mark VI armour featured many refined systems and additional redundancies. In addition, they also featured better stealth systems and compartmentalized systems which were easier to replace. It was named "Corvus" after Corvus Corax, the Primarch of the Raven Guard, as the XIX Legion had been the one to field test the Armour, and it still remains the preferred armour among the Sons of Corax, both in honour of their Primarch and their emphasis on stealth.

Mark VII: Aquila/Imperator Armour

The most common Mark of Power Armour among loyalist Space Marines, Mark VII armour was still being designed when the Traitor Legions reached the Sol System and seized Mars. When this fact became all too foreseeable, Rogal Dorn ordered the design teams transferred to Terra to prevent the Traitors from seizing it. Mark VII featured completely covered chest and arm cabling, a distinct helmet that provided more protection, a high level of compatibility with the previous Marks, and also bore the Imperial Aquila on the chest, which was first used there to provide quick identification of the Loyalist Marines during the chaos of the Siege of Terra.

Mark VIII: Errant Armour

Essentially a set of Mark VII armour, Mark VIII features fixed armour plates on the chest which further cover the vulnerable neck. By the 41st millennium, Mark VIII armour is severely limited to either Captains or Sergeants, though the Minotaurs have a pretty large number of them.

Aegis Armour

The Power Armour of the Grey Knights, Aegis Armour is master-crafted on the forges of Titan and inscribed with prayers and wards to prevent Daemons from possessing it. Based on parts from Marks Vi, VII, and VIII, equipped in the breastplate of each set is a copy of the Liber Daemonica. They frequently have psycannons on their left gauntlet for combat.

Sisters of Battle Armour

Less bulky than the Space Marine armour, as they're worn by normal sized humans, the power armour of the Orders Militant of the Adepta Sororitas provides the same ballistic protection that Space Marine armour does, and gives them enough enhanced strength to carry bolters in combat.

Whatever the Hell Titus's Armor Is

In Warhammer 40000: Space Marine, the Marines are wearing what looks like regular Mark VII Aquila Armor. However, it appears to be far less bulky in comparison to similar armor portrayed in official artwork or Dawn of War, suggesting it might be different. For one thing, it appears to be much more streamlined, with lower pauldrons that aren't quite as fucking enormous, and with more head room and mobility in the arm sections. This becomes very apparent when using ranged weapons, like the Bolter.