Yotha-Hem

Yotha-Hem was one of the 369 Ogdru Hem, the children of the Ogdru Jahad. It is presumed to be the entity that afflicted the survivors of an expedition to the hollow regions within the earth.

Frankenstein Underground

After his encounter with Hellboy in Mexico, Frankenstein's Monster found his way into the underworld and was captured by the inhabitants there. Brought before their master, a man named William, the Monster learned that an expedition into the hollow kingdoms beneath the surface had been organized by the Heliopic Brotherhood of Ra in 1889. William, an American soldier who had experienced apocalyptic visions of a world consumed by war, had been chosen by the Brotherhood to create a colony in the underground along with several of the Brotherhood's top scientists, in order to ensure mankind's future when the surface world became uninhabitable.

William's expedition met with disaster due to the monstrous fauna of the underground, and the survivors sought shelter in an ancient, ruined city of Hyperborea that had sunk under the earth long ago. William's daughter Norah, who had died, was revived by the power in the city, and the survivors were able to stay safely in the ruins to avoid the underground creatures. Soon human inhabitants of the underground made peaceful contact with the survivors, and the two communities began living together.

One of the Brotherhood's scientists among the expedition's survivors, Dr. Lubitsch, went searching through the ruins for secrets of the Hyperboreans' mastery over Vril. In doing so, he freed the spirit of an Ogdru-Hem that had been entombed in the body of a fallen Hyperborean priest. The Ogdru-Hem possessed the body of William and enslaved the people who did not flee, killing his fellow expedition survivors and their spirits to the city and sparing only the life of Dr. Lubitsch as a servant. Norah was killed a second time by her possessed father, her spirit the only one that escaped.

When Frankenstein's Monster discovered the history of the city and how William had become possessed by evil, he struck a deal with Dr. Lubitsch. The doctor, still fascinated by Vril, discovered the energy existed within the Monster as well, and attempted to use it to revive Norah. William arrived and attempted to stop the experiment, enraging the Monster, who used the Vril to kill Lubitsch and then turned it upon William. The Ogdru-Hem abandoned William's body, freeing him from the entity's control, and then manifested in physical form to attack the Monster. The Monster eventually discovered one of the seven daughters of Thoth hidden in the city within a statue of Hecate, and upon freeing her she unleashed the Vril to destroy the Ogdru-Hem, topple the city, free the trapped spirits of the expedition members including William, and transform the underworld into a verdant garden paradise, her spirit inhabiting the realm together with Frankenstein's Monster.

Name

The Ogdru-Hem entity possessing William is not named outright. During a scene taking place before the fall of the city, Hyperborean priests that became dedicated to Hecate's worship invoked the Ogdru-Hem, including an entity named Yotha-Hem. This is presumably the same Ogdru-Hem entity that appeared to attack Frankenstein's Monster.