The Moment of the Magician — Alan Dean Foster

Far to the south of the peaceful Bellwoods, where Jon-Tom the spellsinger continues trying to master the art of turning music into magic, a sinister force has awakened: a magician with great ambition and unheard-of power. He summons lightning to do his bidding, commands an army of faceless flying demons, and claims to come from another world�"one Jon-Tom suspects might be his own. If he can somehow reason with the unknown magician, perhaps they can combine their talents and find a way to go home together.

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Wary of this new wickedness, Jon-Tom's suspicious mentor sends the spellsinger and his companions on a journey to the southlands, assuring him that the land they are to visit is “tropical, friendly, and largely uninhabited.” As Jon-Tom learns all too often, in this mysterious world much will be proven catastrophically wrong.