Random Adventure Generator

ThemeAction/Adventure
This is the most common and straightforward sort of adventure there is. In the Action/Adventure scenario, you present your characters with a task and then confront them with obstacles to overcome in order to accomplish the task successfully.
GoalProtect Endangered NPC(s)
One or more NPCs are in danger, and the characters must protect them. They might be doing this for a reward, or because one or more of the NPCs is a friend or relative of the character. You need to decide what the characters are protecting the NPCs from. The NPC might be a wealthy or powerful person being sought by assassins or kidnappers. The NPC might be a whole village of peasants who are being terrorized by a bandit chieftan.
Story HookHero Offended
Someone greatly offends the hero, so much so that he'll pursue his offender right into the adventure. (Note that this usually means that the offender is a minion of the Master Villain. You'll have to decide whether the minion offended the hero precisely to bring him into the adventure or just as a side-effect of his ordinary villain activities.)
PlotAccumulation of Elements
In this sort of plot, the heroes have to go from place to place -- perhaps covering very little area like a city, perhaps roaming the known world -- and accumulate elements to be used against the Master Villain. These elements may be clues, pieces of an artifact, evidence, or allies.
ClimaxDivine Retribution
Here, the heroes' goal has been to alert the gods that the Master Villain threatens them or their plans; in the last scenes of the adventure, as our heroes face an overwhelming enemy force, the gods bring down their divine retribution on the villain, causing a massive earthquake, tidal wave, lightning storm, or flood of monsters. This is all well and good, but the heroes are too close and must escape the fringe effects of this awesome disaster. A variant on this is the Natural Disaster. No gods are actually involved, but the Master Villain has been tampering with the delicate forces of nature. He may, for instance, have been powering his master spell with the energies of a volcano. When the heroes attack the scene of his spellcasting, the spell goes out of control and so does the volcano. The villain is consumed in the eruption and the heroes must escape or be consumed themselves.
General SettingCosmopolitan City
Most of the story takes place in a large, sophisticated city; center the villain's plot and activities around that city. This setting is best suited to adventures involving more people than monsters; most of your villains should be human or demi-human.
Specific Setting IMadman's Fortress
This is the citadel of a major enemy: Strong, unassailable, filled with soldiers and monsters, lined with secret passages and deathtraps; not a wholesome place for adventurers to spend their time.
Specific Setting IILost City
This is the remnant of some lost civilization or expedition, still thriving in some forgotten corner of the world. Remnants of lost civilizations can even inhabit cavern systems beneath campaign cities, preying on the above-worlders for their goods, slaves, and sacrifices.
Master VillainCorruptor
The Corruptor is the villain who wants to make something nasty out of something that is currently nice. He may be working on a small scale -- i.e., wish to corrupt one character or a few characters, particularly PCs and their favorite NPCs. Alternatively, he may be a big-scale villain trying to change an entire city or nation into a jaded, debased pit of sin, hatred and death.
Minor Villain IMisguided Moralist
This fellow has been convinced that only by helping the villain achieve the Master Plan can he improve the world. He tends to be encountered all through the adventure's plot, usually escaping from the heroes and taunting them for their wrong thinking. Fortunately, he's no more effective as a villain than he is as a thinker.
Minor Villain IIChildhood Friend with a Dark Secret
This Minor Villain is like the character of the same name from the Allies and Neutrals section. However, the heroes find out early on that he's really working for the Master Villain. He may not wish to be helping the villains; his family may be held hostage, or he may just be too frightened of the villain or otherwise weak-willed to refuse. Alternatively, he could actually be evil now.
Ally/NeutralChildhood Friend with a Dark Secret
One of the heroes is accompanied by one of his childhood friends... but said friend now has a Dark Secret. He does strange and mysterious things (sneaks off to send messages, or behaves strangely around certain NPCs, or is scared to death of certain harmless animals or situations) and will not explain why to his PC friend until late in the story.
Monster EncounterForeshadowing Monster
With this monster encounter, combat may not be necessary. This monster encounter exists to alert the characters to the fact that something unusual is going on, a foreshadowing of their upcoming conflicts with the Master Villain.
Character EncounterSeducer
One of the characters is invited to a romantic liaison with an attractive local. This local can just be interested in a brief tryst, could fall madly in love with the hero and follow the hero through the rest of the adventure, could be a Loving Deceiver monster encounter, could be a thief and rob the hero blind, or could be a spy or assassin working for the Master Villain.
DeathtrapStampede
Should the heroes ever cross plains or prairies, their villainous enemies may wish to stampede a herd of large animals at them. Alternatively, beasts in the forest may be stampeded by fires set by the villains; in this case, it will not be one sort of animal charging through, but a mixture of terrified forest animals, from the smallest fox-cub to the largest bear.
ChaseHorseback
This is a relatively short chase -- it only needs to go on for a mile or so before even the best horses are winded. If it goes on longer than that, the horses may collapse and perhaps die.
Omen/ProphesyInnocent Fulfills Prophecy
An innocent could fulfill a prophecy -- one which endangers his/her life. This innocent might, for instance, be the one who is supposed to slay the king, but is not a mighty adventurer able to protect himself from the king; the heroes may find themselves sheltering and helping this poor dupe.
Secret WeaknessElement
The Master Villain can be banished, dispelled, killed, or otherwise defeated by some of element or item. The Master Villain tries to get rid of all the examples of this element in his vicinity; he doesn't let his minions carry it or bring it into his presence. But he's not stupid; he doesn't announce to the world what his weakness is. He tries to hide his concern within another command. If he's allergic to red roses, for instance, he orders all "things of beauty" destroyed within miles of his abode.
Special ConditionTime Limit
Finally, the most obvious condition to place on an adventure is to give it a time limit. If the Master Villain is going to conclude his evil spell in only three days, and his citadel is three hard days' riding away, then the heroes are going to be on the go all throughout the adventure -- with little time to rest, plan, gather allies, or anything except get to where they're going.
Moral QuandryRespect Quandry
This is much like the Ally Quandry, only at a greater distance. The heroes have been utilizing the aid of two (or more) powerful NPC allies. Now, in the course of the adventure, the heroes come across a task which can be accomplished in one of two ways -- say, through military intervention or by esoteric magic. The problem is, the NPC allies are arguing for different choices, and the one whom the heores choose against will no longer aid them.
Red HerringArtifact that Doesn't Work
Often, epic quests against powerful Master Villains require that the heroes find some legendary artifact, the only object which can defeat the villain. If your heroes have had no trouble getting to the artifact -- they've effortlessly sliced through every obstacle you've put in their path and are confidently advancing on the resting place of the magical item -- you can have it not work.
Cruel TrickWanted by the Law
One final complication, one which occurs pretty frequently, is when the heroes are wanted by the law. When they're wanted by the law, they have to travel in secret and very limited in the resources they can acquire.

Based upon tables from the Dungeon Master's Design Kit by TSR, Inc.