Demon X(A/N)th is the source of ALL MAGIC in Xanth. The Magic of Xanth seeps from his sleeping body into a giant rock, which the inhabitants of the Magic Dust Village beat into dust and blow all over Xanth. He recently took Chlorine as his Consort and fathered Nimbus.
Nimby stands for "Not In My Back Yard". It is Demon Xanth's alternate form of a dragon-headed donkey. He lives in the nameless castle, and grants wishes to those that don't know his power. Chlorine talks for him, because he doesn't like to concentrate on minutiae.