|Voiced by||Erik Gunden|
The Mountain Spirit lived on Haunted Mountain. When Haunter and Mysteria led the Ghostbusters on a chase from London to Petronia, Prime Evil told them to lead them through the Haunted Mountain, saying that he would make sure that the Mountain Spirit would take care of the Ghost Busters once and for all.
After being chased by the Spirit, Jake Kong Jr. asked Tracy the Gorilla to produce an answer from his Ghost Pack. Tracy pulled out the Freeze-O-Matic, which Jake immediately used to turn the Spirit into solid ice. According to Eddie Spenser Jr., it would take the monster a week to defrost.
Upon their arrival in the Kingdom of Petronia, Jake revealed to Prince Otis that Haunted Mountain was almost solid gold, and that the gold belonged to the people of Petronia. However, no mention was made on how the gold was to be collected from under the nose of the Mountain Spirit after it had defrosted itself.
Duke Fenwick first appeared in the epsidode Train To Doom-De-Doom-Doom.