Nurglings make their first appearance in the series in Warhawk. Cute little buggers - even Typhus is charmed.
But then, after Mortarion becomes, err, indisposed, thanks to the Khan’s biting insults blade, the Marines suddenly see the Nurglings differently.
“At that, Typhus retrieved two objects from the fly-swirled depths of his armour. Or maybe they retrieved themselves, for they were creatures of some kind, fat little things, pocked with sores and boils, with mouths that took up almost all their bulk. They were noisy when they moved. It sounded like they were giggling, or whispering to one another, or just spitting and slobbering. They wobbled up to Typhus’ outstretched palms, one on each, and grinned at each other.
Crosius found himself instantly captivated. They smelled strongly, and were as hideously ugly as any dream-goblin of his imagination, but he had to fight not to take them both up into his arms, to pet them, to stroke their spiny backs and fondle their horned scalps. “What are these?” He asked.
“Fragments of the god himself, it appears,” said Typhus, sounding uncharacteristically affectionate himself. “The tiniest reflections, but they are appealing, no?”