[ Matt's brain goes nnnngh. ]

Well ... so far, at least, I don't think anything like that has happened. The Shard-Bearers who were possessed or mimicked by shadow creatures came back from dissipation without any lingering effects that anybody's aware of.

As for the people who've been presumably eaten, it does occur to me that there's a way to potentially figure out where they are. If we could get our hands on something that belonged to them.