The adjective macabre is used to describe things that involve the horror of death or violence. If a story involves lots of blood and gore, you can call it macabre.
This word first appeared in English in the context of the "Dance of Death," recounted in literature as the figure of Death leading people in a dance to the grave, and translated from the Old French Danse Macabre. The Macabre part of the phrase is thought to be an alteration of Macabe, "a Maccabee," an allusion to the Maccabees, who were a Jewish people who led a revolt against the Seleucid Empire about 166 B.C.E. and were martyred in the process.