Umbrogaan, sometimes called the Moon Demon, is the older brother of Riven the Stargazer and cousin of Cirogaan the Golden. During his youth, he adopted a human name, Arturo, which many of his kin regarded as quite peculiar and even some thought it an atrocious aberration of his true nature. The affectation, however, proved to have some permanence — he has gone by Arturo exclusively for well over two hundred years. He took this name in grief from the first human companion he had when he was younger, who died tragically during a display of the demon’s more ferocious predisposition.

Arturo is an inquisitive, clever, and highly unpredictable creature. He is most energetic, lustful, and occasionally even violent in the presence of direct moonlight. He stepped into the human realm for the second time when Remy Rocher found the Worn Drachma that belonged to him along the shores near Marseille, France where a known Nexus Point of the Overneath existed. Though largely fond of humans, no amount of time spent in their company has dissolved his confusion at some of their customs and rituals.

Arturo vowed to ward off the cancer growing in Remy’s body in exchange for his love, thus initiating a pact that was truly unique. This mystical bond was later purged by the demon hunter Se-Yun Park, causing the sudden death of Remy. A mourning Arturo transformed into his feral form, or True Demon Form, and went on a violent rampage in an attempt to find Park and was nearly successful in murdering him.

When Remy’s soul was restored and his body partly returned to the living world, Arturo was pacified and the pair fled into the Overneath to live together as Remy had promised to keep Arturo from harming anyone else.

Arturo was strongly against Cirogaan’s plan to move against Amir Tatakera and, in particular, his pursuit of the innocent Milo McKinney. He encountered Milo in the Overneath; he and Remy sheltered Milo for a time until Milo fled for fear of Cirogaan finding them and unleashing his wrath upon them.