Caleb will be investigating, because magic items to steal or make unwise bargains for, plus Sins & Virtues to pump up his magic with, will keep him busy for approximately forever.

Joscelin I haven't decided yet. He could investigate and have a Proper Theological Respect for everything in a way most Travelers won't, or he could infiltrate as either an Angel (almost certainly Cassiel) or one of the militant Peregrines. I'll decide once I know more about what his CR is planning!