When The PCs Don't Realize They're The Villains...

[Smoss]

I was hoping for some PCs being unknowingly evil as well. I pulled that off a while back thanks to a book of prophecies. My PCs saw all the horrible things the book talked about and rushed off to stop the bad things from happening. Unfortunately, each problem was CAUSED by the arrival of the PCs (The half-elf in the party being an insult to the elven town, etc...)

They did not realize at first how much trouble they were causing (It was often subtle). However, when they learned the prophecy book they were following had been written by the big bad guy they put 2 and 2 together. It was the most beautiful moment in my time as a DM. The characters were pissed at the bad guy for fooling them and went on the hunt. They could only blame themselves for following a written prophecy without even thinking to question it...

Oh, and a prophecy might help solve your problem...

 

[MortalPlague]

How are you going to handle the reveal?

The dragon's arrival will be the reveal. He'll demand to know why they haven't upheld their agreement, and then there will be a fight. Afterwards, I don't know if we'll have enough time to wrap up the schizo subplot. Perhaps the angry controlling entity shows up and attacks them? It would be a nice one-two boss punch. Especially deadly if they go nova on the dragon...

 

[dm4hire]

I think you should do Ladyhawke on them and have an eclipse happen and their alter egos seperate, joining the dragon, as he fights against them.

Another approach that might work and cause some interesting roleplaying is to reveal that they were subject to an amnesia spell that only works part of the time. The party is actually evil but via the spell were suppose to be changed to good. As for proof to their true nature when they defeat the dragon, who was actually a minion, they discover a portrait of themselves revealing their true evil nature within the room the dragon was guarding. The portrait could be the key that was needed to break the spell.

 

[Xphile]

I don't know if we'll have enough time to wrap up the schizo subplot. Perhaps the angry controlling entity shows up and attacks them? It would be a nice one-two boss punch. Especially deadly if they go nova on the dragon...

You could also use them as part of a different plot you are running with these players (as part of your normal or a new campaign), have these "NPCs" come to the player's new characters and beg for help.

 

[vagabundo]

This reminds me of a Stephen King novel - the Dark Half I think. Maybe you could rip something from there.

But you really need a solid foundation for why this has happened so you can allow the players to work out how to counter their own Dark Halves.

 

[Rampaging Lawn Gnome]

May be able to rip from the movie Angel Heart as well.

The main character is hired to investigate a missing person (I think) and after he interviews various suspects, they are reported dead. It is revealed at the end that he was the one doing the killing. The person that hired him was also the one from whom he was running (the Dragon in your case).

 

[MortalPlague]

You could also use them as part of a different plot you are running with these players (as part of your normal or a new campaign), have these "NPCs" come to the player's new characters and beg for help.

The main campaign is run by a different DM, so this isn't an option.

I'm worried that by putting too much into this, it won't get resolved in the space of two sessions. I think a simple 'dragon dies, the demon shows up really angry about his foiled plot' might be best, simply for the sake of having a conclusion.

 

[haakon1]

Could do the reveal of the evil alter ego with a mirror, a la "Army of Darkness".