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.
While travelling near the edge of a forest the air is filled with the wailing of battle horns. Soon a large group of mounted cavalry will gallop by in a panicked rush. Some will spot the party and shout "Flee! Flee for your very lives!"
Several minutes later, hundreds of running infantrymen will be spotted. A large group of white clad knights fiercely chanting a battle song is in full pursuit. One of the white knights carries a banner of a white horse on a black background. The horse is rearing under a gold crown, indicating the presence of the Paladin Prince. As the horrified infantrymen struggle to flee into the forest, the zealots charge into their midst and cut them down by the tens and hundreds.