*good grief! I just looked at this before clicking "Post". It's huge! I'm not sure anyone really cares about the tangents I went off on. I'm not sure I really answered the question. Oh well, I wrote it, I will post it.*
Hmm, interesting topic alsih2o. OK, I will toss in my ideas. First, I will talk about my past campaign. Then, I will talk about my current campaign. If one of my players is reading this, I would suggest that you avoid the conversation about the current campaign so you don't spoil any of the surprises down the road for you.
In the last campaign, I had quite a few BBEG's. There were three major story arcs and several minor story arcs that the PC's could pursue.
Minor Story Arc - The Gold Dragon Algalarond has somehow been captured by the Green Dragon's council. The PC's only contact to Algalarond is the magic sword he sometimes uses to speak with them. They picked up the sword in a small adventurer test he long ago setup. (Gorgolands Gauntlet - Among other things, I tweaked names.) BBEG - The Green Dragon's council. They have a treaty with their neighbors, the Gnomes and the Halflings. This is a cold-war style treaty where both sides are rebuilding for the "big push" that might eventually come. The PC's never pursued this story arc, so the Green Dragon's Council never played much more than a flavor role.
Major Story Arc - The Yuan-Ti are invading through an ancient Portal. The PC's first encounter the Yuan-Ti influence through a Spirit Naga minion in the Village of Orlane. The Naga was the minor BBEG for the story plot. The Yuan-Ti abomination Cleric is the BBEG organizing the invasion on this side of the Portal. This was a relatively simple plot to overthrow. The Yuan-Ti were still in the stealth stage of their plan. The PC's were the only ones that knew about it and eventually made their way to the stronghold around the portal. If they had let it go on longer, it would have been much more fun with Yuan-Ti trying to infiltrate kingdoms, etc. But, I have to give the players credit for dealing with it early. The highlight of the encounter with the BBEG was after the battle when the party cleric went into the temple and swore to destroy the Yuan-Yi god. He called on his god to witness his oath. It was a great RP scene and in reward I played it up. In the end, the PC's destroyed the altar, sealed the portal and went home to tell the local Lord what was going on. The Cleric PC bound himself to travel to the Yuan-Ti homeland and make good on his Oath. Fortunately, there were still other things going on, so he was able to wait for a while.
Major Story Arc - The Cleric's family is cursed by a power Devil Lord that is simply known as the Lord of Deception. Nobody knows it's true name. At the beginning of the game, the PC left his home as am emmissary to a new kingdom. He always wanted to be a cleric, but he could never get clerical powers. That is, until he left and found the true god he was worshipping. The Lord of Deception setup an elaborate con. He would emulate the Church of Pter (The Crusader, the Protector, Defender of Good) and use the children of one of Pter's Priests to his own end. The Cleric PC, Aaron, was one of these children. His older brother Jack is the current High Priest, for a false temple. Aaron's younger sister disappeared years ago in the goblin raid that killed his father (thus setting up the false church, etc.)
It took the PC's most of the campaign to learn anything close to the truth of all of this. Mostly after they had unwittingly helped fulfill the end goal of the Lord of Deception. They freed the Hammer of Dol Manul (a powerful, vile, evil artifact), let it get into Jack's possession and then allowed Jack to think he was protecting the Hammer from evil by planeshifting to his god's plane. Jack was pleading with Aaron to stop serving Evil and to come back to him when he decided he must keep the Hammer out of Aaron's hands and planeshifted right in front of him. Too bad Jack was the one who was deceived and his god's home plane was in Hell. The players loved the scenario. The PC's hated the results.
There are insinuations that the Green Dragon's council were aided by the Lord of Deception to entrap Algalarond and to destroy an Earth Power. It is also possible that the Yuan-Ti were just beginning to hurt the Green Dragons when they PC's stopped them. The question is beginning to arise as to whether stopping the Yuan-Ti somehow helped the Lord of Deception. One of the players is starting to worry that this might affect the current campaign, which is 1000 years afterward.
Major Story Arc - There is a slumbering god of Evil, Madness and Chaos trapped in the land. This is one of the big sources of evil. Mhata Nahal's essence is trapped in a demiplane that partially exists with the Prime. His dreams create evil. Some of the good gods want Mhata Nahal out of his slumber and are hoping they can orchestrate his severance with the Prime. You see, Mhata Nahal never had the opportunity to create his own domain when everything was being created. There is a slight risk that if he awakes, he could exit to the Prime and claim it as his domain. Enter the PC's. They will be the lynchpin in all of this. Assuming they willingly agree to enter the demiplane, wake up the god and risk their lives to seal the gate, eliminating the exit to the Prime. In the meantime, you have a displaced Nalfeshnee bent on carving up his own niche of the Prime. Thus enters the visible portion of this story arc.
The Nalfeshnee has figured out how to channel Mhata Nahal's essence to empower undead. He also hates the Lord of Deception, and Pter. He kidnapped Aaron's sister, broke her mind and encouraged multiple personalities to exist. He trained her as a defense against Pter's High Knights and then set her loose on the world. Why? He's evil and he needs somebody that can operate as a wild card while he works with a couple of lich's to raise some massive armies of undead. Evilynn (I kid you not, this is how the player spelled his sister's name in his background. With a name like that, and a history where she disappeared but still appears in his dreams, do you blame me for taking advantage of that and messing with the player a little?) keeps appearing with the armies of undead that are moving north. This leads the PC's to assume she is the BBEG. She is a ruse! Muhahahah. Later on, they figure out the real BBEG is the Nalfeshnee coordinating the rituals that help protect the undead. They disrupt the rituals and do their part in obliterating the lich generals and other undead nasties in the army. Oh, and they helped save evilynn and fix her mind so she isn't MPD anymore. Now, she has to live with the memories of what her evil aspect did, but she is helpful to the PC's.
End result for the campaign - Lord of Deception got his artifact back; Yuan-Ti invasion thwarted; undead army stopped and destroyed, including two 18th level lichs; Nalfeshnee had his powerbase ripped out from under him; God of Chaos, Evil and Madness awoken and made active in the cosmology. Boy, that just sounds so bad doesn't it?
OK, the game was not based on the Cleric PC. It was actually centered around a few other PC's. It just happens that Aaron's background flowed very smoothly into the bad stuff. Thus showing that the curse of the Lord of Deception is not to be passed off lightly. The cleric PC was actually 2nd - 3rd string in importance. On the good side, the PC's helped the gods get bad juju out of the land to make the whole world a happier, better place! They saved the city from the undead armies. They did a lot of good and the game ended on a very strong up note. I just managed to finagle enough things in there that I have plenty to work with for the next campaign.
Summary
BBEG - Yuan-Ti cleric
Underling - Spirit Naga
BBEG - Lord of Deception (Devil Lord)
Underling - Delusional Jack, the cleric who thinks he is worshipping a good god.
BBEG - Nalfeshnee trying to become king
Underlings - Crazy Evilynn, two different Lichs
BBEG - Green Dragon's Council
Underlings - Well, green dragons of assorted ages
-=* Current Campaign *=-
The current campaign is still in a growing stage. So, the BBEG's are not as apparent yet.
On one hand, there is a Green Dragon that the PC's have encountered in the Realm of Dreams. They don't know where he exists in the real world, but they do know he is annoyed with them. He has been asleep for nearly a century and seems to be trying to assault the Realm of Faerie through dreams.
There is the party's first employer. He was looking for people that could be used to create tension and problems for the local feudal hierarchy. His plan is to gain more political power for his Guild, and for himself. The PC's are a ragtag group of mercenaries whose sole purpose is to be inept and cause problems for other people. The PC's don't know this yet. Heck, they might still think he would help them if they needed it.
There there is Mr. Conroe and his wife. They chose a house in a area that is plagued by undead. Poor folks. When reports came in that people had seen a wagon filled with bodies near their manor, the PC's were sent to investigate. No big deal though, it was just a group of zombies that Mr. Conroe and his two lackeys took care of. Why were they in a wagon? Why, to bring them from the far side of the fields over to the firepit. Cremation is the approved method of dealing with the dead in the area and Mr. Conroe burns all undead he deals with.
The PC's searched the manor in the middle of the night, no undead. One of them even sneaked into the Conroe's bedchamber in the middle of the day. Still no undead. Though, he did find some regalia that sounds like it might be used for odd religious practices.
What a coincidence that the house happened to go up in flames shortly thereafter. The Shaman could detect some sort of spirit from hell in the area. All the people in the fields had their necks slit. Mr. and Mrs Conroe were presumably inside when the fire started since that is the last place the ranger was able to track Mr. Conroe to. The PC's couldn't prove any wrongdoing, but aren't really happy with the outcome.
What's really happening? The PC's missed the secret tunnel leading to the nearby valley where Mr. Conroe practices his martial arts, and his new-found necromantic talents. His wife is a devil worshipper (and she favors trickery and deception as two of her strongest tools - bonus points if anyone can guess which devil she worships). The PC's have served as a speedbump in the Conroe's plans for regional conquest. But, the Conroes are having their revenge. They are orchestrating things to make it seem like one or more of the PC's are werewolves. A yeth hound or two mutilating commoners and then tracking thier prints near one of the PC's, before flying away, is creating an interesting tension. Discredit the PC's and get them out of the way, then return to regional domination.
The Conroes are just cogs in the machine that is cranking away across the continent. Nobody is quite sure who is behind a lot of bad things that happen. Even when they do find out, it's hard to correlate it to something bad elsewhere happening. There is no widespread conspiracy and if there is, it was those guys over there. The Lord of Deception works behind the scenes when he can and I promised the players that there would be some political inrigue in this campaign.