The artist, who has tackled the hero for Marvel in the past, will contribute art for the show's line of merchandise and its official programme guide.
"I've worked on some mind-blowing jobs over the past ten years, but this one might just take the cake. It's a biggie," Horn said. "They were nice enough to fly me up last month to see the show in person, and that really helped me get a grasp of the show's scope and look. I've never seen anything like it... a visual spectacle."
Despite rumours of a sixth delay, Turn Off The Dark is scheduled to open later this month. It was previously reported that comic writer Roberto Aguirre-Sacasa has been hired to rework the show's story following scathing reviews of preview performances.
The musical opens to the public on March 15.