Relevant items that a character considers very important can be fair game, yes!

The creatures will not do harm to their owner, but most everything else is fair game -- for instance, they may try to fling someone's treasured item down the well, even if they know their person loves it, because it Needs to Go. So anything up to doing physical harm is possible to happen -- ultimately, protecting their person is still going to be more important than getting rid of things, though!