A skill nearly lost, world-walking belongs to those who can simply walk from parallel world to parallel world. Sometimes the What remains of the Saqalu. They still wield the awesome power they always did, but they are no longer… stable. A Broken Guardian is as likely to take your life... More are born with this ability; some of the Dream have it, too, and a few members of the Kin.
There’s rumor of at least one World-Walker who can also somehow walk through time, but that’s completely unsubstantiated.