The Phanfasms appear to be wild creatures, with the heads of various mammals, birds, and reptiles. They have hairy humanoid bodies and wear minimal clothing. They generally carry primitive weapons, like clubs.
Phanfasms have very powerful magic. They live in one of the most luxurious and splendid cities ever built by magic, but to outside eyes it appears to be a barren waste of rock heaps.
The Phanfasms are ruled by the bear-headed First and Foremost.
For a long time, the Phanfasms kept to themselves, living in solitude on Mount Phantastico. When the Nome King decided to attack the Land of Oz by tunnelling under the Deadly Desert, General Guph enlisted many allies for the invasion, including the Phanfasms as well as the Whimsies and the Growleywogs. When the general first came to their land, the first Phanfasm he saw had a head of an owl.
Since the Phanfasms' magic can provide anything they want or need, Guph recruited them by reminding them of the joy of making happy people unhappy, and the pleasure of destroying innocent and harmless people.
The Phanfasms agreed, planning to conquer the Nomes and their allies after the conquest of Oz. However, when they invaded the Emerald City from a tunnel that was dug underneath the Deadly Desert, Ozma filled it with dust. They thirstily drank from the Forbidden Fountain and forgot all their wickedness. Princess Ozma sent them back to their homes with the Magic Belt. (The Emerald City of Oz)
Paul Dana provides an origin story for the Phanfasms in The Law of Oz and Other Stories, as well as an example of a reformed Phanfasm. Edward Einhorn also features a good Phanfasm, as well as a second invasion of Oz in his book The Living House of Oz. In the upcoming book Fionna Freckles the First and Foremost, by Randy Hoffman, a history of the Phanfasms is presented following the events of The Emerald City of Oz, which offers an explanation for the reformation of some Phanfams on Mt. Phantastico.