Slavery is illegal in Westeros but that evil institution is very much alive and well in the next project from Game of Thrones creators David Benioff and D.B. Weiss.

On Wednesday, HBO announced plans for the duo's first post-Thrones project. They will write and executive-produce Confederate, an alternate-timeline drama in which the South successfully seceded from the Union and slavery is not only legal but has evolved with the times. And a new American Civil War looms.

After the seventh and final season of their Emmy-winning fantasy series is complete, Benioff and Weiss will trade scheming nobles, sell-swords and brothers of the Night's Watch for slaves, slave hunters, abolitionists, politicians, journalists and CEOs of slave-holding corporations.

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“We have discussed Confederate for years, originally as a concept for a feature film,” the duo said in a statement. “But our experience on Thrones has convinced us that no one provides a bigger, better storytelling canvas than HBO. There won’t be dragons or White Walkers in this series, but we are creating a world, and we couldn’t imagine better partners in world-building than Nichelle (Tramble Spellman, who was a producer on CBS' The Good Wife) and Malcolm (Spellman, a writer/producer on Fox's Empire), who have impressed us for a long time with their wit, their imagination and their Scrabble-playing skills.”

“As the brilliant Game of Thrones winds down to its final season, we are thrilled to be able to continue our relationship with Dan and David, knowing that any subject they take on will result in a unique and ambitious series,” said Casey Bloys, president of programming for HBO.

Production will begin after Game of Thrones wraps.