For those unfamiliar with the Hellboy comic book and movie series, let me provide a very quick overview: Hellboy is a demon from Hell, brought to earth by Nazi occultists during World War II. He was saved by the Allies and raised as a son by Professor Trevor Bruttenholm, and later went to work for the secret international Bureau of Paranormal Research and Defense (BPRD), founded by Professor Bruttenholm. His two closest friends and partners are Liz Sherman, a human who can create fire with her mind, and Abe Sapien, an amphibious humanoid.
In Blood and Iron, the BPRD is asked to investigate a haunted mansion purchased by a billionaire who wants to make money from it as a tourist attraction. They learn that the mansion is haunted by ghosts, witches, werewolves and hellhounds and that the evil undead Hungarian countess and vampire Erzsebet Ondrushko, who Professor Bruttenholm has tangled with before, is back to cause more trouble. Ondrushko appears to be based on the real-life historical figure Elizabeth Bathory, and Greek mythological figures Hecate, goddess of the crossroads and witchcraft, and harpies are also thrown into the mix.