Is there a way to roll a morale check for an opponent to see if they back out of combat or flee from a more powerful adversary?
There used to be, but in 3rd Edition they did away with the Morale Check and suggested the GM simply let the NPCs "decide" in character based on the particular situation. The mechanic was revisited in 3.5's Heroes of Battle; and most opponents presented in the Adventure Paths have a 'Morale' entry that describes their conditions for retreat.
Ah. Thanks!
To be more specific:
There ARE effects to force someone to flee. For example, several spells cause "Fear" - when someone is hit by such a spell and fails his Save, he MUST run away; he has no choice. But that is not the same thing as fleeing because your morale is low.
Unlike a Fear spell, low morale leaves you free to make a choice. No matter how low your morale gets, you are free to choose to continue fighting or to run away. There is no game mechanic to force anyone to do anything just because they have low morale - the GM decides for the bad guys and the players decide for their own characters.
In my last game session:
We walked into a flooded room below water level, in a magical air bubble that was part of the room. There was some coral nearby, in the water. We could easily reach into the water. Our one and only main-tank-damage-dealer poked the coral and ended up disarmed and paralyzed as some hidden monsters attacked. They dragged him into the water to drown. Our gunslinger also go paralyzed in the surprise round. Those were the only two damage dealers in the group. We also had me, basically a rogue but with limited damage output, a cleric who isn't built for battle, and a wizard who was kinda low on spells. All 4 monsters were still unhurt and both of our only damage dealers were out of the entire fight.
Suffice it to say that I expected a TPK. I was sure the tank was dead; even if we lived we couldn't likely go in there and save him before he drowned. I was cut off and surrounded with no way out but to go deeper into the dungeon alone, through a locked door that I would almost certainly die before I could pick the lock. No escape.
And those monsters could paralyze any of us in a single hit.
Maybe the cleric and wizard could flee, but the two paralyzed PCs and the trapped PC (me) were doomed for sure. The tank's player was already discussing with us what his next character would be.
My morale was lower than I've had in several years. My character was sure he would die. He was considering trying to flee with acrobatics but expected to fail that too; it would have taken a miraculous roll.
Despite all of that, the wizard and cleric were working to save the paralyzed gunslinger and I decided I had to help them.
Despite my character's low morale and the fact that he was certain he would die, he pitched in and helped. He managed to make his saves vs. the paralysis and he even managed to get a lucky critical that mostly turned the battle around for us. We all lived, but some of us were below -10 HP at the end of the fight.
My point?
If there was ever a time when low morale should have forced someone to flee, or even caused a die to be rolled to see if he would flee, that was the time - I'm very glad there is no such mechanic in this game. Heroes are free to be heroic and even NPCs are free to fight on in desperation against all odds, if and when the GM decides they should.
That was a great encounter!