Decimators (AKA FUCKING AWESOME!) are an unaligned Daemon Engine and look like badass versions of Daemon Knights. Decimators are armoured with slabs of tainted ceramite and adamantium, and a low-set ‘head’ which gives the Decimator a characteristic hunched posture which exudes brooding and vicious menace.
Decimators are a hellish amalgamation of human and xenos technology fused and brought to unholy life by the darkest Warp sorcery and dickery. While they are rarely encountered due to the amount of fusing between compatible human, xeno and daemon technology, when they appear, you better clench your butts. If you want to find them, go to the Galactic South of the Segmentum Tempestus in the benighted reaches of the Nightmare Rifts. Here in the dark void beyond the borders of the Imperium, some unknown source, it is believed, barters these dread killing machines for a high price in blood, plunder and souls - meaning that they are a not only a Daemon Engine, but a mercenary Daemon Engine who will pledge loyalty for the biggest prize of gore, loot, and ballbusting sex. Fucking Awesome.
Decimators, being the badass motherfuckers they are, are able to carry and field a wide range of terrible and rapetastic armaments, such as rapid-firing Butcher Cannons, multi-barrelled Stormlasers, Soulburner Petards, Heavy Conversion Beamer, and great raking Siege Claws, to name but a few.
Towering over even the mighty Contemptor Pattern Dreadnoughts of the Adeptus Astartes, the Decimator is believed to be an attempt to bolster the ranks of such ancient devices that still serve the Traitor Legions. If this is the truth, then it is feared that many warriors of the Imperium will fall before these deadly war machines.
And did we mention that they look fucking cool?