The movie is a big-screen adaptation of Stephen King's book series of the same name.
The text in the image read, "Remember the face of your father."
"I am Roland, son of Steven, son of Henry, true descendant of Arthur. And I have not forgotten," the 43-year-old actor wrote in the caption, adding the hashtag #TheDarkTowerMovie.
"The Dark Tower" revolves around Deschain (Elba), a sort of frontiersman knight whose primary weapon is not a sword, but a pair of revolvers. He sets on a quest to save his dying world by reaching the tower that stands at the nexus point in time and space.