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.
The party is walking through the forest at night when they come upon a clearing. Half a dozen black-robed corpses lie scattered across the ground, and a pentagram of blood is shoddily drawn in the dirt.
It seems these people summoned something they could not control. Whether or not the demon returns is up to the GM, but it would be just as rich if the demon never returned, and for the rest of the night, every stray sound or odd shadow will be jumped at!