Power Armour - Mark IV Maximus Power Armour: 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.At the Mark IV stage of power armour development, Space Marine armour began to take on an appearance recognizable to that of contemporary power armour patterns in the 41st Millennium, its primary change being the abandonment of the separate abutting plates of armour in favour of larger, inflexible armour casings incorporating flexible joints.This marginally reduced an Astartes' mobility but was far easier to produce and maintain, and the suit was actually lighter and provided its wearer with more overall mobility due to the lessened weight, while not reducing the actual level of protection the suit provided compared to its Mark II counterpart.Technical secrets from the Age of Technology recovered on newly conquered worlds during the Great Crusade allowed the Mechanicum to develop this more efficient pattern of armour, improving the quality of protection and reducing the suit's weight at the same time.Improved armouring of the suit's power cables allowed the main arm and chest power supply cables to be safely relocated to the exterior of the armour, making it the first suit to have this feature, while the use of new materials reduced the size and number of cables. The various systems contained within the suit's backpack were miniaturised and made more efficient, allowing the new Phaeton Pattern backpack to be smaller, lighter and to make use of an altered exhaust system that provided a shape much closer to that of the later Mark VI and Mark VII patterns of armour in widespread use by the Firstborn Astartes of the 41st Millennium.The Mark IV suit's helmet was a completely new design, the basic shape inspired by the sweeping front of the Mark III. In the Mark IV and later patterns the helmet was no longer fixed to the armour's neck plates, but moved with the wearer's head while still maintaining an environmental seal. This advancement represented the Artificers' increasing experience with neural connector gear and the new materials which flooded into the Martian workshops as the Great Crusade progressed.Whilst standard patterns of armour were shared across the Space Marine Legions during the Great Crusade, variations on these templates surfaced in most of the Legions.For instance, Mark IV Achean Pattern Power Armour arose as a local variation of Mark IV Maximus Power Armour, produced for the Thousand Sons Legion by the forges local to that Legion's homeworld of Prospero. More stylised than their standard armour, Achean Pattern battle plate was most often worn by XVth Legion Veterans.The Praetor Pattern was a Mark IV variant used by the Ultramarines during the Great Crusade and Horus Heresy. Produced at Veridia Forge, an asteroid-based Mechanicum mining base in the Veridian System, it was not an accepted mark of the greater Legiones Astartes by the time of the Battle of Calth.Mark IV power armour was envisioned at the time to be the ultimate and final type of Space Marine armour, able to offer the best protection in a variety of conditions. Many of the Space Marine Legions were entirely or partially re-equipped with it by the start of the Horus Heresy in the early 31st Millennium.As a result of its widespread production and use prior to and during the Horus Heresy, Mark IV suits are the most common of the pre-Heresy relic armour patterns still in service with the Adeptus Astartes of the 41st Millennium. Notably, a few Chapters, such as the Red Scorpions and Iron Hands, are still capable of producing new Mark IV suits in the 41st millennium.This pattern of armour is the type of power armour still worn by most of the original Chaos Space Marines of the Traitor Legions, as they usually have access only to the technology they took with them into the Eye of Terror ten millennia ago. However, some Chaos Space Marines mix and match more modern pieces of armour with their ancient Mark II and Mark IV suits to replace damaged portions.Those Space Marines who have turned Renegade since the Horus Heresy obviously wear the power armour that was current to the era when they first turned against the Emperor. Heretic Astartes often strip more modern pieces to upgrade their armour from the bodies of Loyalist Space Marines killed in battle.Among Loyalist Space Marines of the 41st Millennium, being granted the right to wear a relic suit of this ancient form of power armour is a great honour and such an Astartes will be given greater respect than normal by his fellow battle-brothers and even Space Marines from other Chapters.