How can I make my PCs flee?
The party is in the woods searching for a macguffin, when they happen across an evil sorcerer sacrificing humans for a summoning ritual. He summons some lesser deamons to slow down the party. When the party kills him, or he kills the hostages, a dragon is summoned by the spilled blood. The thing is, the dragon is surprised (it could be in a bath-towel-and-shower-cap caught unaware).
The problem is my players will think "Oh so we're fighting a dragon this week", when they should actually run away after realizing the enemy is too powerful for them, especially that they got the macguffin they came for.
As usually my players just bash on 'till the creature is dead, how can I use the creature to show them that it is not the mission objective without buffing it up or making it completely invulnerable.