They had caused the changes. He had heard of similar changes coming over grey seers after prolonged consumption of the stuff, and the Horned Rat alone knew how much warpstone dust he had breathed in since the foolish dwarfs had taken their stupid airship out over the Wastes.

If only he had stayed below in the cupola, where it was safe. Where the air was filtered by screens, there was plenty of food and human and dwarf magic protected you from the effects of Chaos. Alas that had not proved possible. His thirteen-times-be-damned master, Grey Seer Thanquol, had insisted on regular reports and it was impossible for his sorcery to touch his lackey while he was within the protected area. So Lurk had to leave the protection of the gondola to please his accursed master. Thus had Lurk come to be exposed to the mutating dust in the first place. And now, with the cupola full to bursting with stunties, it was all but impossible for Lurk to hide down there. It would only have been a matter of time before he was detected, and he doubted that even a skaven of his prodigious potency could overcome so many dwarf warriors.
He did not know what was worse — the pain in his head or the hunger that burned in his belly. He could not remember ever being so ravenous, not even after battle, when every skaven was most in need of sustenance. The hunger had come on him with the changes in his body. He was huge now, and muscular, in a way he had never been before. He had muscles like a rat-ogre and his tail was like a length of steel cable. His body was probably twice its previous size and his talons were like daggers. Knobs of horn, similar to the ones on Grey Seer Thanquol’s cranium, had started to protrude from his skull. Was he becoming a grey seer, Lurk wondered? Or was this a sign of some other blessing from the Horned Rat? Right at this moment, Lurk did not feel particularly blessed. Right now he was feeling tired and hungry and sorry for himself. He was filled with the justifiable caution in the face of his enemies that some mistakenly called fear. And there was this strange buzzing in his head. A buzzing that seemed to take the form of words.
Lurk! You dolt! Is that you?
Lurk wondered whether this was a hallucination brought on by starvation, or whether the horrors he had endured had finally driven him mad. Still, there was something strangely familiar about the voice, an annoying arrogance and a contempt for everyone but its owner.
Lurk! Answer me! I know you are there! I can sense you!
Lurk’s paws strayed to the amulet Grey Seer Thanquol had given him. Was it possible, he asked? After all these long days, that Thanquol had managed to re-establish contact?
I can see the airship, you oaf! And I can feel your feeble mind. If you do not answer me, I shall consume your pathetic soul, and feed your festering carcass to Boneripper.
The first faint flicker of rebellion flared in Lurk’s brain. Who was Grey Seer Thanquol to speak to him in such a manner after all he had endured? Had Thanquol ever ventured into the Chaos Wastes? Had Thanquol ever travelled so far in such a dangerous and experimental vehicle? Had Thanquol ever been exposed to warpstone dust and mutated in such an uncontrollable fashion? Just let him try and feed me to Boneripper, Lurk thought, as the rage built up in his mind. I will tear the creature limb from limb, consume its flesh, crack its bones for marrow and spit the gristle at you, mighty Grey Seer Thanquol. You see if I don’t.
But what he did was reach out and touch the crystal. “Mightiest of masters,” he chittered. “Can it really be you? Has your omnipotent sorcery finally succeeded in overcoming the dire obstacles placed in its way by those wicked dwarfs and re-established contact with your faithful Lurk?”
Yes, idiot, it has!
The baleful thought blasted through the ether and lodged itself in Lurk’s brain. Lurk was amazed that his mouth and forebrain could mouth such gross and insincere flattery while his hindbrain and entire spirit festered with rebellion. He knew that given a chance he would kill Thanquol, and the world would be none the worse for it.