One thing that I can't help doing is worldbuilding. It's like breathing for me. As a result, there are some things I already know about the world of the Black Blood of the Earth, even though play has not yet started.
One of those things that I know about is the Portals. No one is entirely sure where the Portals came from, though legends speak of strange men with grey skin and powerful magic the likes of which has not even been matched by the Blood Sorcerers. Not all of them seem to work any more (though some can be induced to work through the power of the Black Blood of the Earth), but the ones that do work reliably allow instantaneous travel across the continents. It's said that some Portals, hidden in caves, underground cities buried by the passage of millennia, on uninhabited islands, or deep in trackless swamps, travel to different worlds entirely. Perhaps a Portal can be found that leads to a fabled land beyond the sky like lizard-filled Torsh, Oerth, modern Earth, the Majestic Wilderlands, ancient Barsoom, maybe even the Dreamlands or dread Carcosa.
Of course, there are other ways to get to the worlds beyond the sky, such as the Skyships. Powered by magic and the Earth's Black Blood, these ships can fly into the sky and beyond, to the edges of the crystal sphere and through the mysterious, fiery phlogiston to other crystal spheres containing other worlds. The phlogiston flow to Oerth is particularly well-traveled, but other spheres have contact with the Black-Blooded Earth.
[EDIT 17 AUGUST 2012] None of this will be included in the final world. The themes involved can't include other worlds to which the people can escape. I may move these ideas to the Terra Ultima setting instead - or I may have to make a new world setting to use these ideas.