The clerics at the church believe that the baron has been acting somewhat strangely of late. Rumors abound of a snake-like "thing" in the sewers under the castle. A chilling, sinister voice is sometimes heard echoing from the dungeons late at night, speaking an unknown, demonic tongue.
Meanwhile, the baron's behavior becomes more bizarre. He begins arresting innocent people, raiding the keeps of other barons and dukes and raising taxes to a slavish height. He even begins hiring adventurers and sending them off to remote regions on secret missions.
The sooner the characters get to the bottom of things, the better. The baron is likely to start a local war with his antics, if not a peasant-revolt first. And there is no telling what he sent those adventurers off to find.
Somehow, the characters must discover that a Water Naga has taken up residence in the flooded caverns under the castle. It has used enchantment spells (geas, charm, etc) to control the baron for its own purposes.
Confronting and killing the Naga requires getting past the baron and all his men, the castle's defenses, the Naga's traps and defenses and fighting the creature in deep, murky water.
A cowardly spirit naga is ashamed of that condition (most spirit naga are pretty brave] and wants to get some courage. It is sure the party has some solution for its problem.
Just to encourage them, it has Charmed a few people important to the party and now offers a deal, the party does as told and the naga doesn't kill anybody.
The naga will be happy to accompany the party as they attempt to instill courage in it, during which time it will usually run away from any minor danger, or rush into any major the party was trying to avoid.Of course, once they do gain courage for the beast, it may well be brave enough to attack the party...
The group's friend has been poisoned by a rogue assassin and now they need an antidote. The group's cleric devined that they require a scale, some poison and blood of a dark naga. When the group finds its domain they may attempt to barter with it, but the naga will be constantly detecting the thoughts of the group and will most probably use them for some task of its own before trying to kill them.
The party's mentor has been assassinated by a rival warlord. Fortunately, local legend tells of an ancient jeweled skull that will resurrect the dead. Unfortunately, the skull resides in tomb on a small island (3 square miles in area) named Naga Island located on the inland sea.
Luckily, most of the naga have long since died out. Apart from some lethal vegetation and plantlife, the party finds the tomb amidst a wild garden of orchids.
Unluckily, the tomb is watched by a trio of large Guardian Naga. The guardians will warn the group to leave the island within 2 hours. If the group attempts negotiation, it will repeat the warning 2 more times. If the party do not follow the naga's direction, the guardians go looking for group -- after they destroy the party's means of transportion to the island.
The nagas will use obscure spells to confound the party, and depend heavily on fireball and lighting bolt spells to inflict large amounts of damage. In addition, they will make judicious use of their poison and spit abilities to weaken the group and prolong their suffering as punishment for trespassing.
A CE enemy of the party is suffering the dream-haunting attack of a night hag. So he wants the party to confront her. He is free with promises to reform and/or pay the party, none of which seems at all reliable. (There are a variety of ways to enforce those promises, but by definition, he has access to stronger magic than the party does, and so no way to be sure.)
There are suggestions of waiting until he has been weakened further, or even killed by the hag before attacking her. Some have suggested she be allowed to escape with his soul. While possibly effective in dealing with the threat of the enemy, there are worries this is evil, and there is an outside chance he will honor his promises.
The paladin's new mount seems to have come with a price: two nightmares who have a brooding hatred for the good and noble horse. One is standard; the other is ice-based. They will take turns with fly-by attacks and and harrassing techniques until they can kill the horse, and possibly the party that protects it.
The noble mount, knowing that these creatures are bound by evil, will not attack them out of sympathy for their condition.
The peace conference has a rule that no magic weapons, armor, etc are to be present. Of course that does not please all parties, and one employs a nightwing which converts all the magic into non-magic. Once inside the conference, a few dispel evils converts them back to magic and their users are in fine position to dictate terms.
The party of course learns of the plot, possibly almost by accident, and must expose it, and defeat the nightwing, who won't get paid if the plot fails.
A guild of mostly low-level magicians has been collecting scrolls for years, storing them in ceramic tubes mostly. They have counted on being able to support themselves financially or defend themselves valiantly with the huge supply of scrolls.
A mediocre sorcerer got himself out of trouble with a nightwalker by swearing to him he knew the location of a very old and powerful scroll stored amongst the hoard.
Using a combination of stolen magics, the nightwalker is sneaking into the storage area every night and killing whoever guards it. He then searches through scrolls, crushing all those that do not meet his needs.
The magicians are quite alarmed by this, and have ceased even guarding the stockpile. They know he is in there: they can hear him crushing tubes and reading scrolls. But THEY aren't going in after something like that...
The Fortress of Night only exists during the hours of darkness, and seems invulnerable to all means of entry except mundane walking to it. Unfortunately none of those who have tried that have managed to return, and it may be that none have even managed to reach the Fortress. However, the Fortress has the artifact the party needs...
A Nightcrawler lairs in front of the entrance, and will be very happy to welcome the party.
A wealthy baron has created a huge natural reserve for hunting. He wanted it to be particularly nice, so he has spent tens of thousands of gold pieces creating a 20 acre paradise. Unfortunately for him, this has attracted the presence of a Nymph who now dwells in the center of the reserve. She is not sympathetic to the baron's desire to hunt and all attempts at negotiation have ended with the baron's men being blinded (thankfully there have been no deaths).
The party must reach some accommodation between the two. Convincing the nymph to even talk to the baron will require a Diplomacy/Bluff check of DC 15. From then on the party will have to assist the two sides in reaching a compromise.
(One possible compromise is that the baron only hunts predators like wolves and leaves the other animals alone.)
Once this is done the party has a new problem: at some point during negotiations the baron has become smitten with the lovely nymph. How the party handles this twist is the topic for another day.