Grenville doesn't see it. I do. The Withered WILL be back for its fetish – we need to finish our work here and move on. Perhaps one we could handle, but when it comes, I do not think it will come alone – when they swarm, they're like locusts, consuming everything and everybody in their path.
I feel they are watching us, but the why of it I don't know. Are they waiting to see what Grenville's efforts yield with the sphere? If so, that is a further cause for concern. If he unlocks their purpose - might they somehow make use of it? And to what end?