Some places in the half astral plane are known only by legend and rumor, with no widely known way to get there.
The Great Atlas lists such places as Terrae Obscurae. His Excellency offers bounties for confirmed routes to Obscure places, newly discovered places, and new routes to known places. Addenda to the Atlas are published at irregular intervals.

The crown offers higher bounties for routes to especially tantalizing places. The rewards often include knighthoods, titles, even peerages. Generally there is no negotiation about the value of a route in such cases; an imperial "offer" is pretty much unrefusable. But there has always been something of a black market in prized routes. Private parties have been known to exchange princely sums for secret routes. The practice of withholding routes from the crown is not illegal, but is regarded as poor sportsmanship.