So don't remove it completely? :X I'm sure it fits somewhere in the necro spell arsenal.
I'm not an expert on them, but I'm sure scent of the murk could be renamed and added to regular spells and this one incorporated into one of murk spells or maybe, as mages get summon spectral silk spell from another Murk quest (Morbid Curiosity), necros could get the pet who used to wear those clothes.
(Yeah, i'm no good at brainstorming right after waking up, but I'm sure you've already thought of these things, so I'm showing some moral support.)