The Summoner of Ghosts was a human man.
A charlatan from the 16th century, this supposed sorcerer claimed that he could summon ghosts and spirits from the beyond (for a price), an effect actually obtained thanks to smoke-and-mirror effects such as a primitive magic-lantern (with the help of a sometimes-lazy apprentice). Benvenuto Cellini, a famous Italian sculptor, was interested in spiritism and the supernatural, and once paid the Summoner to make a ghost manifest before him, at midnight, in the Coliseum Ruins in Rome. Through the use of a magic-lantern, the charlatan did make a ghastly face appear, and, satisfied, Cellini paid him in gold as agreed.
Behind the scenes
The Summoner first appeared in flashbacks in the 1957 story Mickey Mouse in Magic Land.