After an
exchange of owls, Selvetarm had been inspired: if he couldn’t kill Vhaeraun here, he could still swamp him in spiders. They held special significance for the pair of them, and were - due to the significance on Selvetarm’s end - quite a convenient species as plaguing went.
He didn’t have direct access to Vhaeraun’s blood for tracking, but they shared blood, and for once that worked in Selvetarm’s favor as he eventually figured out how to use his own to imprint on the spiders in its stead, directing them to seek out something similar but not exactly identical. He spent another few days fine-tuning the degree of similarity, spent a bit more time summoning them into his locked room in Gryffindor until they coated the walls and floor, and finally sent them to Vhaeraun by way of the ceiling. Then he summoned and sent off another roomful in a different direction in case someone incinerated the first lot before they reached their target. Then, a smile taking hold and beginning to spread, he prepared and dispatched a third.
A while and another two swarms of spiders (plus one swarm left in his room for backup) later, Selvetarm decided he had enough for now and seated himself in the common room, cleaning his knife, with his sword and mace propped against the chair waiting their turn. His smile remained wide and he was, quite unbeknownst to himself and to his certain horror if he’d known, on the verge of humming gaily.
((Assuming Vhaeraun’s eventual arrival is after whatever other conversations may take place. Feel free to have others notice the spiders))