Nerundill caught hints, snippets of conversation. The rumors surrounded a book, a book of magnificent power. A book that contained the knowledge of the ancients. With every new tantalizing bit of information he heard, his resolve to possess this book increased.
In the middle of an unimportant combat with some bandits a burst of wild magic transforms all of the PCs and their opponents in to random animals and monsters. They retain their intelligence (though not, of course, the ability of speech). They can either carry on the combat in their new forms, panic, or otherwise react how they see best. After about an hour, they return, unharmed, to their normal form.