The Theros world-building panel at PAX has just begun, and although there aren't any full-card spoilers yet, the panelists have provided tantalizing glimpses of art and flavor that we haven't seen yet. The most concrete one was an image of a beautiful woman in an elegant chiton, surrounded by pigs that, according to the Nyx starfield projected on them, have been enchanted. This is, of course, a reference to Odysseus's crew being turned to pigs by the enchantress Circe when they are stranded on her home isle. I would speculate the final card will look like this:
Wildland Hexmistress 1WW
Creature - Human Wizard (Rare)
Whenever a creature an opponent control attacks, exile it at end of combat and its controller puts a 2/2 green Boar creature token onto the battlefield.
As the panel rolls on, keep checking back here for further Theros updates!