He was said to be the main villain of the film, but the marketing didn't show him at all. (superfans.website)
Cumberbatch was one of two actors who brought to life the dread Dormammu, Strange's comic book arch-nemesis, and the secret, secondary villain of the film alongside Mads Mikkelsen's Kaecilius. (newsarama.com)
However, we do get to see a bit more of Jordan's Killmonger, who is set to be one of the main villains of the film alongside Serkis» Klaue. (screenrant.com)