The Last Continent (Discworld #22)

There’s big trouble at the Unseen University, Ankh-Morpork’s lone institute of higher learning. A professor is missing–and the one person who can find him is not only the most inept magician the school ever produced, but currently stranded on the unfinished down-under continent of Fourecks.

As the UU faculty tries to bring him back, Rincewind is having troubles of his own, thanks to a pushy mystical kangaroo trickster named Scrappy and a mob of Fourecks hooligans who are out to hang him. All his problems would be solved if he could just make it rain… for the first time ever. And if the time-traveling professors can get to the right millennium…