Seriously, what is with the welcome wagon lately. They're slacking.

"Rifts are - I guess they're not much different to wormholes. They're tears in the fabric of the universe, cracks in space and time - that kind of thing. Sometimes things slip through the cracks. ... Sometimes people slip through the cracks. These people are called Wanderers."

A.k.a, Cora. And well, they're called other things, but Wanderers is the friendlier term.