I've posted this one a few times, but it was still darn fun:
1) BBEG, a Lawful Evil wizard who is one of the ruling caste from an evil town, shows up at the party's home, unguarded and unprotected.
2) Party drags him inside, prepares to kill him.
3) BBEG begs them to hear him out -- and shows them a special amulet he's wearing. It's set to send out a signal at midnight to a matching amulet in the assassin's guild. If he's alive, it sends out a "no worries" signal. If he's dead, it sends out a signal that tells the assassin to order and carry out the horrific torture and mutilation and execution of someone close to each member of the party -- family member, girlfriend, link to forgotten past, etc.
4) Party swears and hears BBEG out.
5) BBEG begins talking about a NEW evil that is coming, and how the party and the BBEG need to team up to stop it, because it's worse than either of them.
6) BBEG mentions the name of the new evil, which the party has heard once or twice but not in any meaningful way.
7) BBEG pauses as if lost in thought, coughs twice, keels over, and then explodes in a gigantic fireball.
8) Party begins adventuring in real time (1 minute game == 1 minute real life) to get to the assassin's guild and stop the executions from being sent (they're sent magically to the distant towns where these people live).
9) A lot of death and destruction later, the party reaches the head of the guild with one minute left, orders him to destroy those orders and not carry out the assassinations.
10) Assassin says, "What are you talking about? I don't have any orders like that."
The BBEG had been bluffing. He faked his own death in order to get them to take out the assassin's guild.
Oh, how they laughed...
- - - - -
In a followup story, I recently used the BBEG again -- he had actually died, but had a simulacrum prepared. A lot of adventuring later, he had seemed to atone and turn good, helping the party against the new evil -- which was indeed very evil and worse than the BBEG himself.
As the party prepares to head out and confront an evil menace with a powrful magical artifact, the BBEG announces that he's leading a team to take back his city -- this time, for the power of good. The Lawful Evil hierarchy has been moving towards Neutral Evil, and he has seen the error of his ways and is now Lawful Good. The party wishes him luck, and the BBEG sets out with some of the party's friends to take his town back.
The party heads out to confront the big evil. They get there and team up with a whole mess of allies. While waiting for the big evil, they talk with one of their friends, who tells them that he's found out, via scrying, that the former BBEG wizard has taken back his town -- in an enormous bloody combat that killed hundreds of innocent citizens. He has also apparently sacrificed all of the party's friends to his dark god in atonement and has crowned himself emperor of the world.
The party grinds their teeth and promises to take him down as soon as they're done fighting the evil menace.
Evil menace arrives. Combat ensues. The party can't beat the evil menace themselves, but they manage to get close to the magical artifact, the key to the evil menace's power.
As they close in to destroy the artifact, they hear the voice of the BBEG in their heads, telling them that they MUST not destroy the artifact, that it would be VERY BAD to destroy it.
"Right, screw you, we know you're evil again," says the party, and destroys the artifact -- which could only be destroyed by forces of good. Its destruction gives the evil menace a huge amount of power and new abilities. He laughs and departs.
The BBEG had indeed taken over the city, but without killing innocents. He was still good. He didn't sacrifice anyone. The friend that they'd learned all this from was a minion of the evil menace, feeding them disinformation.
Oh, how they laughed...
-Tacky