I'm not fond of "terror", but am OK with dropping pair. Freyar's pretty good with names for collectives of critters. Let's see what he suggests.
Well I'm not that attached to terror, so we might as well change it.
Assuming we can agree on something else!
Of the collective nouns of worms I don't mind a knot or squirm, if we can't come up with anything original.
Hmm, a twist of devil wyrms? A warp of devil wyrms?
I'm leaning toward squirm at the moment.