Find the missing Defaced Sisters

We met a strange woman at the barbarian camp – something of a mix between a priestess, a witch, and a sorceress... Or maybe she's simply an impostor? Whatever she is, she says her three sisters went out to search for who-knows-what, and never returned. She hinted vaguely that if we were able to find them, she'd aid us in our search. It's a faint trail, but it's better than nothing!