The Magic Goes Away
Larry Niven
 The Warlock, whose actual name is both unknown and unpronounceable, is a powerful sorcerer in excess of 200 years of age. He observes that when he stays in one place too long, his powers dwindle and will return only when he leaves that place. Experimentation leads him to create an apparatus (now known as the Warlock's Wheel) consisting of a metal disc enchanted to spin perpetually. The enchantment eventually consumes all the mana in the vicinity, causing a localized failure in all magic. The Warlock realizes that magic is fueled by a non-renewable resource, which would cause great concern among the magicians, as it was through their magic that nations enforced their wills both internally and abroad. The widespread diminishing of magical power in The Magic Goes Away triggered a quest on the part of the most powerful of the magicians of the time to harness a new source of magic (the Moon), resulting in the events described in the book. It was eventually discovered (in The Magic May Return) that mana was originally carried to Earth and the other bodies of the solar system on the solar wind, replenishing mana slowly over time. However, at some point in the "recent" past (a few thousand years ago) a god created an invisible shield between Earth and Sun that intercepted the solar mana and caused the eventual decline of magic on Earth. Traditional fantasy creatures inhabit Niven's Magic universe, but devolve to normal animals when deprived of mana. For example, a unicorn becomes a simple horse. *The Warlock - One of the world's foremost magicians. He devised a simple experiment to explain why a magician's power would fade over time, a device called the Warlock's Wheel. *Clubfoot - The Warlock's apprentice. A Native American named after a deformity of his foot that he could have cured long ago but it would have cost him half his power. *Wavyhill - The first Necromancer. Exploiting the mana inherent in murder, he invented necromancy. His name comes from his practice of building his houses under magically supported overhangs; when the local mana is depleted by a battle, the hillside collapses, trapping his foe and eliminating the evidence at the same time. *Orolandes - A Greek soldier, survivor of the sinking of Atlantis. *Mirandee - A powerful witch, formerly Warlock's lover. *Aran - A werewolf who assisted the Warlock in defeating the necromancer Wavyhill. *Roze Kattee - The God Of Love And Madness. Its power lies in the taking away of love or madness. Enemy Berzerkers are suddenly rendered sane, those who do not worship Roze Kattee never find mates, etc. *The World Worm - Its spine composes all the world's mountain chains, the Andes, Himalayas, Rockies, etc. It consumes its own tail, along with anything that might be living on it. *Yangin-Atep - A fire god. *Coyote, Loki, etc. - A trickster god for many cultures. *Zoosh - Once a powerful patriarch. *Left-Handed Hummingbird - A Mesoamerican god (Huitzilopochtli).