Dusk Caller working as intended?
I don't think this is a bug so much as a (perhaps) misaligned function, but as far as I can tell, when you use the Dusk Caller item it sends your thrall to the nearest cell -- not necessarily yours, mind you, but the nearest cell of anyone in your clan.
While this is amusing and could be fun as an option, it makes the functionality of the item much less useful. For example, if your base is in North Gloomrot and a friend's base is in Farbane forest and you capture a thrall in Dunley Farmlands, your thrall will go to Farbane (as far as I can tell) if it happens to be slightly nearer. This is actually the opposite of useful, as you've increased the distance to get it home.
Please consider correcting this, or even have the suggested use above as an optional "upgrade" perhaps or something you can toggle between self/clan.