This year was a little weird. Since Wizards isn't releasing a "third" set in the traditional fashion, I didn't have a lot to go on. I couldn't try to guess what they would do, and since they set it up as a 2-set block, they closed off a lot of design space.
So, I tried to do it as a set to bridge the gap between the theoretically discrete Morningtide and Shadowmoor. That meant taking the little flavor that had leaked about the upcoming set, coming up with a little backstory and going from there. Thus, a tribal set with a little more focus on the graveyard than the past two.
In story terms, the idea is that the goblin scout Thark, with manipulation from Oona and Colfenor has stumbled into Velis Veil. There, he discovers the source of the Changelings and, being a good goblin, plugs himself into the energy. The resulting discharges - the Aurora - radiate out, warping the plane.
Not too much in here that would make the rules manager cry. We'd need new rules for splice (splicing onto permanents just gives them a comes into play ability), clash (how the "numbers" work) and a few individual cards. The usual caveats apply - focus on limited, may break in constructed (I was pretty good this time, I think). Think of it as the file to be handed off to development, who will immediately point out that Grave doesn't work at all. Still messing with that one...
Here they are. Thanks to the irc guru team for their fixes. Feel free to post comments in the forums.