An Attack Moon was the Imperial designation given to a class of massive Ork vessels that were encountered by the Imperium of Man during the War of the Beast from 544-546.M32. These massive voidcraft served as the flagships of the group of giant Ork Warlords who were each known as The Beast.
An Attack Moon were capable of almost instantaneous travel through a hyperdimensional realm known as "subspace" and was outfitted with a powerful gravitic weapon known as a "Gravity Whip" that was capable of ripping apart even the largest of Battleships or even other planets.
Ork Attack Moons, like the much smaller Roks, were constructed from a core that included the hollowed-out remains of large asteroids and small planetoids or moons. At the height of The Beast's reign of terror in the mid-32nd Millennium, the Orks were capable of using technology that surpassed even that available to the Imperium of Man. The Attack Moons were capable of Faster-Than-Light travel over large distances without the use of the Warp, which made possible instantaneous interstellar travel for Ork forces from one location to another, and were outfitted with immensely powerful gravity-based weapons capable of destroying entire planets.
The hollowed-out moons were covered in a vast pattern of fused wreckage and interconnected metal plates, thick enough that kinetic or directed energy attacks against the moon's surface were completely ineffective. The Attack Moon's most obvious external surface feature was that of adjustable plating capable of moving, shutters the size of inland seas and raised portions the size of entire mountain ranges that were capable of forming the stylised image of an Ork face, and could move in time with the words spoken by the Great Beast. The vast and monstrous tusked maw could stretch open wide, allowing Ork warships and transports to travel outwards from the core of the Attack Moon. The eyes burned with the magmatic light of the moon's core.
An Attack Moon was capable of appearing through subspace closer to a planet than the laws of physics allowed, causing immense destruction upon the world it visited as its gravity field was completely disrupted by the tidal forces generated by the sudden arrival of the massive Ork planetoid. When an Attack Moon appeared over a target world, it emerged from subspace close enough that the sound from its titanic, Ork-shaped maw was capable of travelling to the planet's surface, heralding the arrival of the Great Beast.
Attack Moons were capable of FTL travel through the creation of what were known to the Adeptus Mechanicus as "subspace" corridors, a hyperdimensional realm that existed "in-between" the Materium and the Immaterium. A safer method of travel than through the Warp, subspace travel nonetheless was not entirely instantaneous and did require some travel time, with the arrival of the Attack Moon at its destination in realspace heralded by strange gravitational phenomenon, culminating with the moon flickering in and out of existence until it fully materialised. While transitioning from one planet to another the receiving planet would be subjected to greater and greater gravitational and tidal stress, resulting in sudden climate change, earthquakes and other geological catastrophes.
In truth, an Attack Moon was neither a true planetary sphere nor an independently operating voidcraft. It was actually just the terminus for the Ork subspace tunnel dubbed a "WAAAGH! Gate" by the Greenskins. This allowed it to deploy endless waves of Orks warships and landing craft from the origin point.
Once the Attack Moon arrived in-system, usually impossibly close to its target, the moon would disgorge an endless stream of Ork warships to protect itself and Assault Craft to begin planetary invasion. Once a world was completely under the control of the Orks, a special gravitic nexus facility would be constructed on the planet's surface, a match to an existing facility on the moon's surface. Once constructed and activated, the gravitic nexus would begin the slow process of tearing the planet apart, with massive chunks the size of mountains being lifted into the maw of the Attack Moon, eventually to become part of the moon itself, expanding it and growing it over time.
The Attack Moons of the Great Beast were not just simply massive transport vessels or war machines, but instead they were advanced prototypes, as the Orks sought to perfect their gravitic planetoid concept. The ultimate version of the design, known as an "Attack Planet," was to be finished at The Beast's homeworld of Ullanor, and was intended to attack Terra itself while the smaller Attack Moons served as mere beacons to guide its travel.
The Orks built an unknown number of Attack Moons during the War of the Beast, and several were destroyed by Imperial forces during the war at great cost. Imperial records of that era do not indicate what became of the remaining Attack Moons after the Orks' ultimate defeat at the Third Battle of Ullanor. It is believed that those that remained were hunted down and destroyed by Imperial forces or were ultimately abandoned as the surviving Orks inevitably fragmented and their lessened WAAAGH! energy led to the loss of the technical knowledge needed to build and maintain the Attack Moons.
In addition to the Attack Moon's ability to destroy a world by merely translating into realspace too near the destination planet, it also possessed immense tractor beam emitters capable of tearing a world to pieces, the Attack Moon boasted a considerable arsenal of surface weapons and powerful Void Shields even more powerful than that found on most Battleship-class vessels.
The Attack Moon's primary weapon was a "Gravitic Whip," a massively powerful gravity weapon that took the form of a green tentacle-like whip of energy that struck out towards its target and either tore it apart near instantaneously or wrapped around it and slowly crush it as the gravitic shear intensified. The weapon drew upon the great Ork energy sources buried deep within the vessel, and could be seen visibly charging for attack as coils of green energy coruscated up the pylons that directed the flow of Gravitic Whip energy to its target.
A Gravity Whip was capable of fending off entire fleets on its own, with each flail of the energy whip tearing apart Cruisers with ease, destroying entire wings of Attack Craft and causing untold destruction against larger voidships. Fortunately for the Imperium in the 32nd Millennium, the weapon required a truly massive amount of energy to activate and needed to recharge itself between attacks. This gave Imperial Navy battlefleets enough time to close and engage the moon directly before they could be entirely crushed by the action of the Gravity Whip.
- Warhammer 40,000: Rulebook (6th Edition), pp. 169, 201
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