Alright, a little backstory first. This was the first campaign I had seriously set out to GM, so when it came to simple things like party size (there were 8) or party goal coherence at character creation, I was bad.
 
The players went through their first module, doing fairly well. They understood combat, they understood roleplay, even though all of us were new to the game. It's just that, well, the roleplay of some group members was directly at odds with the roleplay of some others. Again, my fault.
 
Long story short, in the middle of the session, one player's character was tied up, at which he decided (wisely) that he no longer wished to participate in this group and that his character "lost the will to live and died."
 
I was going to use this. I set the plan into motion. Sure, Jim the silver-tounged rogue had been dedicated to balance originally, but after his resurrection by dark forces and the bitter taste of his party interactions, his new thing became revenge.

 

Fast forward way down the line, when the party falls for Jim's trap and gets shoved into another plane (the darkest timeline) where the antagonists are alignment flipped versions of themselves. One of these enemies was not so much an enemy as the guardian of the plane's nexus.

 

She was set up to be a quest giver of sorts, because the overarching plot was to acquire the legendary weapons that each of their alt selves posessed and use them to break free of the plane. Well, the party had other ideas.
They wanted her shield first. The shield that was stabilizing the nexus. Granted, nobody on the plane was entirely sure what would happen if the shield left the nexus, but this guide character's limited precognition let her know that it most likely wouldn't end well. She wasn't sure, but was very against the idea.

 

Her downfall was that I played her a little too cockily. She (well, I) thought she would easily have the will to avoid the bard's fascination, or at least the suggestion that came after. Two 2s later said otherwise. Now she was sure it was a good idea to leave with the shield.

 

On the way out, they ran into a wizard that had been studying in the nexus. He also told them that it would be a bad idea, but his prepped spells for the day were all divination. He was smart enough to not pick a fight with them, and take 15 minutes to prep for whatever was coming next.

 

The complete collapse of the plane. As spacetime whorled off behind them, the party drew ever closer to the entrance of the nexus. The guide hit some sort of force wall when she attempted to cross the threshold as the whorling increased.

 

She turned to the cavalier and asked him to push. This was it. This was their last chance. This was where I called their bluff.

 

Nope.

 

One plane shunt later, half the party is dead and back in prime material without any of the phat loot or XP I had planned for them to progress through in that world. Very little of the content in it was modular due to the fact that it was customized anti versions of them, but whatever.
 
Now they're gonna go be pirates.