Wizard's Holiday
Diane Duane
 When Nita's sister Dairine signs up for an intragalactic exchange program without permission, their local advisors transfer the mission to Nita and Kit. The destination seems to be an ideal planet, and they are hoping for a vacation. Meanwhile, the aliens who arrive at Dairine's house appear to be very "alien". However, Nita's dreams become nightmarish and the planet Alaalu turns out to be hiding a dark secret: an avatar of the Lone Power has been trapped in this dystopia since their people refused Its gift of entropy. While this may have prevented deterioration to war, crime and natural disasters, among other things, it also prevented such change as evolution, and the Alaalu people are trapped in their current stage of existence when they have the potential to be free of it. It becomes the young wizards' job to convince the Alaalu wizard and her people to accept this change, inevitably setting the Lone Power free. On Earth, the wizards at Dairine's place have become aware that their Sun is in danger of flaring up to the point of scorching their planet. However, one of the visitors comes from a planet where he is a guardian against the recurrence of such a disaster, and recognizes it in time for them to save the Earth.