Last Month
I began discussing the hows and wherefores of keeping effective secrets in your D&D campaigns. As part of that discussion, I identified five general categories of secrets: historical secrets, character secrets, divine secrets, geographical secrets, and "just plain weird" secrets. In last month's column I discussed the first two categories and provided a series of examples.

This Month
I'll tackle the final three.

Divine Secrets
Because their nature tends to imply mystery and hidden truth, the gods of your campaign world can often provide an excellent springboard for secrets. Since so many of the fundamentals of your world -- its creation, its history, and its destiny -- are likely to be intimately entwined with the activities of the divine powers, secrets about the gods are often among the most ancient and powerful mysteries you can devise. Of course, the epic scale of such secrets can be a double-edged sword. Plausibly drawing the players into contact with godly entities and their hidden truths can be difficult, not to mention the obvious play balance problems. Cleverly constructed secrets, though, can certainly skirt around these difficulties.

Assuming you do discover a way to pull one off, one of the truly interesting characteristics of a really good divine secret is the sense of power and participation it can lend your players. Little can do more to reinforce the characters' importance than uncovering a deep secret of the gods themselves. Such a discovery tends to almost automatically bestow a sort of legendary status upon the PCs, making the players more fond of their characters.

8. One of the Gods Walks Among Us
In most D&D campaigns, the gods are all-powerful distant beings who live on a remote plane of existence. Under normal conditions, any direct contact between the PCs and the divine powers is extremely unlikely.
This particular secret revolves around the notion that one of the gods secretly resides on the physical plane in the guise of a being or character with whom the PCs can meet and interact. This ploy is particularly effective if a lot of time passes between the point at which the PCs first encounter the disguised entity and the moment when they uncover his secret. It's much more interesting when the secret involves a character with whom the players are quite familiar. The mysterious beggar who keeps turning up along the PCs' route is a much better choice than the fourth guard from the left on that random caravan they passed on the way to the capital city last year.
Another choice that makes or breaks this secret is your explanation of how and why the divine entity decided to leave its home and walk among mere mortals. In most cases, such an undertaking would be extremely out of character for a god. A very interesting and unique set of circumstances should exist to justify it.
My own version of this secret goes something like this: The patriarch of the pantheon (your version of Zeus or Odin) is getting very tired and looking to retire from his divine duties. To find a replacement, he holds a contest among the remaining gods to determine who might be wise enough to replace him. The contest consists of an enormously complex riddle the patriarch devises to test his colleagues' wisdom. The first to solve the riddle shall inherit the divine throne and tend to the mortals.
Unfortunately, none of the other gods manage to arrive at a solution. Still looking to retire, the patriarch decides that instead of passing the throne along to another god, he should simply destroy the mortal world and wash his hands of the problem, leaving him free to retire. To this end, he unleashes a series of six plagues that will eventually consume the mortal realm.
Shortly after the plagues are unleashed, one of the other gods (the favored daughter of the patriarch) discovers the patriarch's plan and pleads with him to reconsider. The goddess tries to convince the patriarch that the mortal world has become a rare treasure, much too valuable to simply cast off. Although reluctant to accept this argument, the patriarch proposes a simple experiment. As a favor to his daughter, he agrees to spend exactly ten years roaming the physical world in the guise of a mortal. If he witnesses truly unique beauty on his travels, he will call back the plagues and continue to serve as lord of the heavens.
This secret opens up plenty of opportunities for interesting gameplay. Beyond the fact that the players get to interact with the king of the gods, there are also the six mysterious plagues to deal with and the possible involvement of the goddess. You might even think of a way to include the patriarch's riddle. Suppose, for instance, that an evil mortal cleric discovers the riddle and devises a plan to solve it himself, hoping to catch the attention of the patriarch and claim the heavenly throne!

9. The Gods are Dead!
As I noted earlier, the gods play a pivotal role in just about any D&D game world. The gods and the religions that have sprung up around them are probably instrumental in defining the culture, history, and tone of your campaign. On a more practical level, the gods are the ultimate source of the magical energies that allow clerics to cast their spells.
Or so everyone believes. Suppose, though, that the gods haven't been the real source of that magical energy all these years. Instead, all the gods are dead, and for some mysterious reason, nobody knows this.
Once again, to do this right, you should wait to spring this particular secret until you are well into your campaign -- probably not until the PCs reach 10th level or above. Although this secret can be quite a shocking and interesting revelation when properly handled, it's certain to have severe consequences for the campaign moving forward. As part of your implementation of the secret, you should prepare yourself to deal with this fallout -- how can there be clerics in a world without gods? How do clerics get their spells?
A decent explanation of how the gods died without attracting the attention of their followers is also in order. I have a couple of possibilities. Suppose the gods were secretly defeated and destroyed by a rival faction of new gods. Ever since the defeat, the rivals have answered the clerics' pleas and granted them spells in the guise of their fallen peers. The rivals believe the original gods failed their followers when they allowed evil into the world, jeopardizing all of creation. By seizing control themselves, the new gods hope to manipulate the faithful into destroying evil once and for all.
Properly staged, this particular variation on the secret should lead to plenty of opportunities for in-depth roleplaying. As an example, think about how a lawful good cleric might react. Once the cleric finally discovers the big secret, she learns that her beloved deity has been slain (itself an evil act), but the usurper plans to bring about an even better world and might just have the power to do so. What role might the cleric decide to play in the unfolding events?
Another possible explanation is that the gods' death was entirely natural. Finally, after billions of years, the heavenly powers grew old and weak. The gods had always hoped that by the time they reached the twilight of their lives, their mortal followers would no longer need their guidance or assistance. Unfortunately, this never came to pass -- the mortals are still at least a couple of centuries away from achieving a truly harmonious civilization. As a final act of devotion, the gods decided to end their own lives a few decades early and drain the last ounces of their energies into a heavenly wellspring. For the last several years, this wellspring has been the real source of the clerical spells granted to the mortal faithful. By draining the remainder of their own lives into the spring, the gods used all their available powers to guarantee that the mortals will continue to receive spells for as long as possible.
Figuring out just how much energy remains in the wellspring is the biggest decision you'll face if you decide to go this route. Is there energy enough for fifty more years of cleric spells? Twenty years? Five years? Depending upon how your campaign is unfolding, it might be interesting to let your cleric characters know that all but their simplest magical powers (such as the various cure spells) will suddenly stop working in the near future. Figuring out how to deal with such a tragedy should prove quite a challenge for an experienced hero. Ideally, though, you might want to allow the PCs to discover a means of reversing the tragedy or recharging the wellspring. Suddenly taking away all of a PC's major powers with little recourse is a great way to frustrate and lose a player.

10. The Champion
Another possibility for a divine secret revolves around a special destiny bestowed upon the PCs by the gods themselves. Allowing the players to discover that one or more of their characters have been specially selected by the gods to perform some important mission is another revelation that you can use to underscore the PCs' importance in the campaign.
My own version of this secret might go something like this: One day, the matriarch of the gods decides that she is too old and weak to sit upon the heavenly throne and desires to retire. Almost immediately after she breaks the news to her fellow deities, a battle breaks out among her three divine children over who is most fit to replace her. Since war is not an appropriate pursuit for gods, the matriarch is ultimately forced to devise a special contest to head off the conflict. She instructs each of the three pretenders to secretly beget a mortal child. She will then see to it that these three mortals come into conflict when they reach adulthood. The winner of the resulting struggle will decide which of the matriarch's children shall sit upon the heavenly throne. The matriarch insists upon two additional rules: Each pretender can aid the mortal child only three times across the course of the mortal's life, and any god who willingly reveals the existence of the contest or the true heritage of the three champions to a mortal is disqualified.
As you might guess, one of the three champions is one of the PCs. Perhaps the first hint of the secret the chosen one receives is a sudden and miraculous escape from danger. Many game sessions later, the PC will discover that the miracle was due to the intervention of his divine parent using one of the three allowable "assists." Properly implementing this scheme also requires you to create two worthy rivals for the PC and skillfully set up a three-way conflict. While this might take a while, it certainly gives you lots of opportunities for interesting adventures and storylines once you've pulled it off.

Geographical Secrets
Secrets about the geography of your campaign world give the players opportunities to discover exciting new places to explore. When I presented my tips for developing local area maps in Dragon Magazine 264 and 265, I noted that it's often handy to have a mechanism you can use to keep players relatively confined to small areas, allowing you to open up new lands when you are good and ready. Appropriate geographical secrets are an excellent tool you can use to achieve this goal. Suppose, for instance, that your campaign area is bounded by a seemingly impenetrable mountain chain. From time to time, though, mysterious strangers appear in the area who must be coming from somewhere beyond the mountains. Eventually, after you've had time to fully develop the area, you can allow the PCs to discover the secret that allows them to pass under the mountains. Such a tidbit can be anything from the mundane (a secret pass known only to the most experienced rangers) to the fantastic (a magic doorway that opens only with the appropriate command word, á la Ali Baba).

Here are a couple of other ideas...

11. The Disappearing Village
Fantasy literature and pop culture are rife with legends of magical cities and villages that only appear under certain special circumstances (Brigadoon, Kaddath, and so on). Although these stories have become something of a high fantasy cliché, such a locale can be a remarkably effective device in a Dungeons & Dragons campaign.
Making this concept work usually boils down to two things. First, you have to make the conditions under which the city appears interesting and exciting. This is a fine opportunity to inject an interesting puzzle into your game. (For the importance of puzzles, see the "Dungeoncraft" installment in Dragon 266.) Even after the PCs discover the existence of the disappearing village, they should still have to figure out how to get there. Usually, this involves being in exactly the right spot at exactly the right time (maybe the village only appears for the first day of each year) -- but calculating the precise place and time might be very difficult. Perhaps the village appears in a different location each time, and the appearances combine to form an intricate geometric pattern. In order to predict the next place the village will appear, the players might have to figure out how to complete the pattern.
The second bit you need to figure out is how and why the village disappears. Is there a magical curse involved? A strange rift in the spacetime continuum? The interplay of powerful divine forces? A nice piece of backstory goes a long way toward capturing the attention of your players, and making the village more than just a cliché.
My own disappearing village might look something like this: Many thousands of years ago, there existed an ancient city that was home to a large and prominent temple dedicated to the goddess of wisdom. So splendid was this temple that it housed the goddess' favored oracle, a mystical pool that allowed the faithful to gain knowledge by gazing upon the images mysteriously reflected in its waters. Eventually, it came to pass that the goddess of wisdom left on a lengthy quest to seek new understanding in distant dimensions. At first, the goddess' absence extended across several years, and later across several decades. Many of the inhabitants of the ancient city began to feel abandoned and betrayed as a result. Over time, their faith in their patron began to wane until the temple was finally dismantled. The oracle still stood, though it was no longer consulted in reverence for the goddess, but in contempt of her. Before long, the oracle was being used for all sorts of unseemly purposes -- everything from grave robbers gazing into the waters to uncover the whereabouts of local tombs to infidels attempting to glean hidden secrets of the gods themselves.
When the goddess of wisdom finally returned from her quest and discovered what had happened to her temple, she was so outraged that she decided to punish the entire city and its inhabitants by banishing them all to one of the frightful dimensions she discovered on her quest. Only a single soul escaped the god's wrath: the only one of the city's 4,126 inhabitants who kept the faith and honored the god every single day during her absence. Because of the loyalty of this single citizen, the goddess of wisdom allows the city to return to its rightful place in the material world one day out of each 4,126 (roughly once every eleven years).
Note that this scheme offers an excellent opportunity to make an interesting puzzle out of the situation. In order to actually enter the disappearing city, the players must not only discover its former whereabouts, but they must also deduce the nature of the city's curse and ferret out its exact population in order to calculate when the city will next reappear.

12. The Message
This one is simple, yet quite strange and effective. It can provide an interesting means of testing the players' memories and perception.
Somewhere on your very first area map, place a lake with a distinctive (though natural) shape. Many adventures later, somewhere in a deep dungeon, the players should discover a pile of scrolls covered in ancient runes that are the remnants of a long-dead language. After the appropriate investigation and analysis, the players might even learn to decipher several of the old runes and pick up some useful knowledge from the scrolls.
It just so happens that the lake from that first area map is in the exact shape of one of the elder runes: the symbol that translates as "danger." There is a powerful extradimensional entity trapped in a crypt at the bottom of the lake. The lake itself was created by the ancient and powerful civilization that trapped the entity, and its shape was selected to warn interlopers.
If you don't call any special attention to the map or lake once the players have uncovered the ancient writings, it's quite likely that it will take them several game sessions to notice your clue. Once they finally do, their reaction (and the series of ensuing adventures in which they attempt to uncover the meaning of the warning) should prove priceless.

Just Plain Weird Secrets
This last category covers secrets that are so unusual they defy description. Most of the secrets that fit into this category are odd enough to have a pretty profound impact on the game world. So much so, in fact, that you should introduce this sort of material with care. Some players really respond to this type of stuff, while others are put off by it. You should probably try a ploy like this only if you know your players all fit into the first category.

Again, the best way to illustrate a really weird secret of this sort is through an example. . . .

13. The Dream
I've borrowed this idea from H.P. Lovecraft. Eventually, after a couple dozen game sessions, the PCs might discover an entirely new fantasy world that exists in their dreams. Each night as the PCs sleep, they have an opportunity to enter this new realm, where they take on personae that are similar to themselves yet different in the way "dreamselves" often are. You can even conduct entire adventures set in the dream realm. Anything bad that befalls the characters there somehow spills over to their actual selves in the "real" world. (Perhaps dream wounds become real through some sort of psychic trauma.) Properly pulled off, this campaign should draw all sorts of interesting parallels between the dream realm and the physical world, and raise interesting questions about who created the dream world and why.