While the upcoming crossover between the cast of "The Unwritten" and "Fables" has been public knowledge for a while, details have - and remain - somewhat thin, but Vertigo pulled back the curtain a little further today with the release of a Peter Gross and Mark Buckingham-illustrated promo -- titled "Unknown" -- for the event. Teasing the meeting between Mike Carey and Bill Willingham's characters in "The Unwritten" #50, the image features Tommy Taylor reaching out toward Bigby Wolf, who's grasping Taylor by the arm.

"There's a paradox at the heart of this story," Carey told CBR in late 2012. "The 'Fables' characters show up in 'The Unwritten,' but all of the settings and a whole lot of the characters in the story will be very familiar from the Fables world. So who's visiting who? It remains to be seen, and the answer is not what you might think at the outset.

"If you're a regular 'Fables' reader, you'll see a lot of your favorite characters, but you may not recognize all of them the first time you see them. And actually, the same goes for the trio of characters from the 'The Unwritten,' who are our main point of view."

Check out the image below and keep locked in to CBR for more on the "The Unwritten"/"Fables"crossover!