Guidance Thrusters - These thrusters provide the variable thrust needed for the Inceptor to control his flight.

As the Great Crusade reached its climax at the dawn of the 31st Millennium and the Imperium reached its zenith in terms of technology and strength, the Space Marine Legions found their original suits of Mark II Crusade armour wearing out. While some Legions chose to continue local production and maintenance, the ancient Mechanicum of Mars designed a new variant, which was to be called the Mark IV or "Maximus" Pattern since it was produced during the days of the Imperium's greatest glory. This suit of power armour was developed by Space Marine Artificers and Techmarines as a solution to the supply problems caused by the Horus Heresy. It was manufactured from the most basic of materials, and it was easy to maintain. Almost all of its users used molecular bonding studs to hold the armour layers of plasteel and ceramite together, and these studs became a distinctive marker of this pattern of power armour. Since the fighting on Terra during this period was primarily close-quarters, the strength of a warrior's chest and arms was of paramount importance. The legs of this armour are not powered at all, but are enclosed in tough padded breaches, though simple steel plates were sometimes also used. Sloped pauldrons, or shoulder plates, are used to deflect enemy fire. Primaris Space Marines are trained to use these angles to deflect shots. High casualties suffered by the Legiones Astartes on these worlds and in other similar, close-quarters environments such as boarding actions and tunnel-fighting during the Great Crusade led to the development by the ancient Mechanicum of the Mark III pattern of power armour. The Mark III was best suited for spacecraft boarding actions and combat in confined subterranean tunnel complexes with little cover.Mark X Gravis Inceptor Helmet - The Mark X Gravis Pattern helmet used by Inceptors possesses an expanded rebreather filter for low-orbit combat drops.

Greaves - Part of the armour that protects the lower leg. The greaves incorporate gyroscopic stabilisers and power units that can magnetise the soles of the armour's boots for combat in zero-gravity or other unstable conditions.Nutrient Reservoir: A self-replenishing high-energy food store that can sustain a Space Marine’s metabolism. Thus during battle, there is no need for a Space Marine to eat or drink. Though quieter than the Mark I, Crusade Armour also is not intended for stealth, though the sight of an Astartes wearing this armour draws every Space Marine's mind to the glory of the Great Crusade before the disaster of the Horus Heresy unfolded and provides a major enhancement to unit morale. This habit of gaining information about a situation by scent is so natural to the Space Wolves that many feel slightly disoriented and claustrophobic when forced by circumstances to don their helmets. The Mark III helmet was loosely based on a medieval frog-mouthed helm, but with a more industrial feel to it. The helmet design was used as the starting point for the helmets worn by the power-armoured Grey Knights models that came out 20 years later. Amongst the Astartes, it is the Space Wolves who are the most fervent practitioners of this custom. In their case, it is no mere show of courage as the Canis Helix gifts them with a preternaturally acute sense of smell, rivalling that of natural wolves or trained scent-hounds.

A Primaris Space Marine Intercessor of the Ultramarines Chapter wearing Mark X Tacticus Power Armour (see text to the left for corresponding numbers).

Mark III Space Marines

Inceptor Pauldron - Pauldrons with a third-layer of armour, compared to only two on the standard Mark X Tacticus Pattern armour. The advanced systems of Space Marine power armour also monitor the Astartes' biological functions, feeding the collected medical information to the wearer and, if necessary, to the Chapter's Apothecaries when he is wounded. It is able to withstand tremendous punishment, and serves as a solid heavy-weapons platform in open-field combat. Due to its size, it is best deployed in close quarters such as the corridors of a starship, where the standard-issue Storm Bolter can be most effective.