Best known for playing Jim Hopper in Stranger Things, David Harbour will star in the film as the titular Hellboy, or Anung Un Rama, a powerful but well-meaning Cambion (or half-demon) who was summoned from the underworld by Nazi occultists and later discovered by the Allied Forces. He then became a member of the Bureau for Paranormal Research and Defence, helping out in the fight against the occult threats.