Abattoir
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The Abattoir is a FUCK HUEG Necron vehicle and is arguably considered as the largest Necron land vehicle to date. Bigger then the Æonic Orb, Crypt Stalker and even the fucking Megalith. All shall shit bricks when this thing goes to town. The Abattoir is so fuckhueg that Imperial forces actually mistaken it for a god damned Necron Building. In fact, a recent review of Imperial records now indicates that the Abattoir may have been encountered on six separate occasions before it was understood exactly what it was. If there ever was a Necron Titan, this would be the closest one would get without getting into Skub territory.
Overview
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Once called World Harvesters by the Eldar (One must wonder what the World Engine was actually called), the Abattoirs are more building than vehicle, and have been responsible for the destruction of many worlds and civilizations. During ancient times these pyramid-sized constructs were used when slave races could not be transported to the temples of the C'tan to be sacrificed.
Unlike most Necron units and vehicles the Abattoir does not have phasing capacities, instead it has to be brought to a world to be deployed on site. This is generally done by a rapid-deployment ship like the Scythe Class Harvester. Once on the surface, it walks around, supported by tentacle-like limbs that are deployed from its capacitor sub-pyramids. This makes it look reminiscent to the Flying Spaghetti Monster which would be hilarious if it wasn't for the fact that this thing dwarfs a Megalith.
The Abattoir as previously mentioned, is the largest known Necron ground vehicle and is of similar displacement to a goddamned Imperial Warlord Titan in size and tonnage. Essentially a large floating city, it has recently been postulated by Imperial theorists that the Abattoir forms the hub of the wheel which is the Necron's teleportation network.
Like most Necron units the Abattoir makes heavy use of Gauss Weaponry, although its armaments are much stronger. An Abbatoir's weapons not only flay their victims where they stand, but also harvest their pain and fear at the moment of death, creating a stored source of sustenance for the captured C'tan to nibble upon like some sort of strange pet project. In addition to these weapons, it carries massive swarms of Scarabs inside; normally used for maintenance purposes, they can also be deployed offensively.
There are no actual official Abattoir models, but that doesn't stop some people from making one.
Gallery
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Praise to be! The Metallic Spaghetti Monster!
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A computer rendered Abattoir.
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Size comparison between the Æonic Orb and the Abattoir.