Unaffected

A trillion spores gave the fog its texture, each one a tyranid organism smaller than a terrestrial mite. As Dante ran into this smoke his armour let out a shrill warning. The tiny sporelings attacked his battleplate, eating into the banded metal of the joints and the soft seals beneath. Where his skin was exposed by broken plate it blistered under the effects of toxin and acid.
...The flaming, silent warriors of the damned Legion fought on unaffected, but they drew away from him, lighthouses in the fog, leaving Dante to his fate.



The Devastation of Baal, Chapter Twenty-Eight