The event will begin in issue #50 of The Unwritten when characters from the comic find their way into the world of Fables.
Fables writer Bill Willingham previously discussed the storyline at New York Comic Con's Vertigo: Cutting Edge panel, where he insisted that it is not a crossover in the traditional sense.
"It's not a crossover, it's an event, takes place entirely in Unwritten," Newsarama quotes him as saying.
"Some of the characters in that book are able to find their way into other worlds, places and books. Starting with issue #50, for five issues, one or more of the Unwritten characters will find their way into the world of Fables. It doesn't go well for everyone involved."
The Unwritten #50 arrives in stores in May.