The Iron Warriors have a special association with the Obliterator cult more so than any other Traitor Legion, and the very first Obliterators were from among the Iron Warriors. It is whispered that the origins of the so-called "technovirus" that created the first Obliterators orignated from non other than Perturabo himself, Primarch of the Iron Warriors.
An Obliterator is a Chaos Space Marine, affected the "technovirus", a daemonic virus that transformed its host into bloodthirsty mutant weapons of Chaos. They are monstrous hybrids of human, daemon and machine. An Obliterator is able to absorb any weapon into its body that is held for too long. These unfortunates can also spawn these weapons from their very flesh, and also grow ammunition for them. The price of such power means that Obliterators are biologically fused to their suits of power armour and weapons.
As a result of their mutation, Obliterators are no longer even remotely sane. This insanity could be caused by the constant mental and physical trauma of absorbing weapons into the Obliterator's body or being biologically welded by his own body to his armour. This insanity is also possibly caused by the Machine Spirits of his weapons and armour fusing into a destructive daemonic entity after infection by the virus.
Obliterators tower over their Chaos Space Marine brethren, and they are usually at least as broad as they are tall, dwarfing even the Terminator-armoured escorts of their lords. Their flesh is stretched and distorted across an exoskeleton of metal and plasteel, and pistons writhe and churn under their sallow skin. They eat ammunition and drink Promethium, it is said, for whatever energies an Obliterator consumes, he can replicate within himself.
Though cadres of the mysterious Obliterators are thankfully rare. There are rumors of Perturabo hoarding a huge army of Obliterators on some world within the eye, bidding his time to launch an attack on the Imperium of Man that will finally topple the false Emperor from his throne.