Indeed, being 'the best' doesn't mean you can't be challenged, especially by those mooks just below you who want a leg up....just because you rule the world with an iron fist doesn't mean those guys a level or two below you (with perhaps better connections!) don't also want it. But in Greek myth, at least "the best" is usually only trumped by the Gods....of course, they can act through a mook (Achiles' Heel and all that), but there is some element of 'inevitability' in their deaths, and this is usually regarded in D&D as 'railroading.'
.....which is why I think trying to mimic myth or literature is not the most productive thing in general for D&D. Even if you get 'mythic,' there's still DM fiat involved in every challenge you face. Heracles, Strongest Man in the World, was only felled by the machinations of a deity; Achilles was the same way. Boromir fell to an epic artefact. Samson fell to a convinient barber. These are all devices of plot, not legitimate challenges, and those who try to use them as challenges are either going to be dissapointed, or are going to be accused of railroading, in general. However, that is a seperate thread.....
In this one, I simply seek to provide a resource for DM's who want to avoid the "silly" in high-level, normal-magic (e.g.: no significant nerfing) D&D. To give advice on how good stories, with the core elements of plot, conflict, and danger, can still be crafted when the PC's wield grand powers, that just because they are powerful doesn't mean that the game becomes all about bigger monsters and more treasure. I want to help DMs and players develop a game in which high-powered D&D characters still must think, still fear the unknown, still have moral uncertainty, still endure arduous journeys, still exemplify heroic sacrifice, and which still has the very same obstacles in the path of the PC's that have traditionally defined a good story. And yes, there are at least a few players/DM's who feel that the above is impossible....not just difficult, but unavailable...in a game with many of the traditional D&D spells being readily available. I'm not discounting campaigns without the magic or 'invincibility' of typical high level D&D campaigns, merely trying to help DM's who wish to run normal D&D continue to run interesting stories into the highest levels that do not fall into the usual traps.
So, here's a few ideas:
Make the Players Think About Things Other Than Survival: It's true, high-level D&D characters can survive a lot of things. Which is why a DM shouldn't be making the players think about survival of their own characters so much as the survival of what they want those characters to be. As you approach epic levels, it's dang difficult to kill a PC, but you can threaten things other than life and limb -- the lives and limbs of their family, the nation, Truth, Justice, Honor, Good, etc. About the only thing that can threaten their life and limb are the very powerful monsters and NPC's, and those can be integral to the plot, just like they are at lower levels. But since just reducing their hp to -10 doesn't kill them any more, the NPC's have to be diabolical about it (e.g.: disintegrating, true destroying, devouring, turning the creature undead, etc.), or not worry about threatening the livelihood....threatening to destroy a village of innocents, or to kill their wife if they move, are risky things...and they don't threaten the hp of any PC.
Play with Expectations: Divinations are powerful tools, but they can be very simply foiled when they would otherwise destroy the plot. NPC's who lie, plans that aren't playing out exactly as the PC's expect, and red herrings are remarkably potent tools in a DM's plot arsenal. Similarly, it's helpful to create situations in which the "right" solution is actually the worst one to have at the time, and remember to play the ideas of deities to the hilt. Divinations can still be useful ("How many enemies are coming?" will help them avoid abmush, "Would it be helpful to prepare
Fireball?" may give them a hint at the weaknesses of foes), but they are not a cure-all. "Whodunnit?" comes up with an unexpected answer (Baron von Butterworth?! But he's dead!!), or the answer they give doesn't solve the true mystery (Well, this thug did the deed, but he's got no motive...), or the usually-simple answer provides very sketchy information. "Who killed the king?" comes up "??" because the king is still alive...but the PC's just know that the divination was incomprehensible. In addition, remember no knowledge is complete. Even the most learned sage in the land can be surprised by a new species of monster they've never met before, or a new cult with arcane practices they haven't studied. Similarly, even if the PC's find out who foreclosed on their mortgage, it shouldn't mean they know how to handle the threat.....if the answer comes up "A Mind Flayer Named Billbob," that should create more questions than it solves.
React: Know what you want the campaign to do. Hinge your adventure on encounters, and events, and make sure you know the circumstances in which they occur. This allows you to mostly allow the PC's to run around doing whatever, but to inject your own ideas in at an opportune moment. A high-level DM without limits on spells has to be able to roll with the punches the PC's throw.....if the plan of the Sahagin Prince is to rule the sea by stealing the Crown of Coral late on a moonless night, that happens even if the PC's decide to Plane Shift - Teleport halfway around the world, or to persue the Great Evil Squid in the Gap...even when the PC's destroy the Squid Who Lurks in the Gap (a kraken who was masterminding the whole thing) before they decide to follow up on the whole sahagin conspiracy, the sahagin steal it...but now don't have a master to give it to. Think in-character about what would happen then....would the Sahagin Prince ransom the crown (setting up the PC's for a dungeon crawl?) or maybe try to use it to unlock the Hellgate himself (setting up the PC's to defend the Coral Palace and it's inhabitants from the beings released?) You may have planned for the PC's to thwart the theivery initially, but they went a different route -- in a high-level game, the risk of this is much higher, and you should ideally be able to rumble with whatever direction the PC's go in. This should mean that either (1) your planning goes to a great level of detail (by the time the idea to thwart the sahagin is in your mind, you have the stats of them, their commanders, the one sending them on the quest, and the creatures to come from the hellgate), or (2) your 'winging it' skills are great (you can open the page of the MM to Kraken, and your PHB to Sorcerer, and determine on-the-fly what the creature is capable of).
There Has to be a Point to the Journey: Getting from Point A to Point B is easy in a high-level game...unless there's a motive for taking the long way around, PC's generally wont' be inclined to do it. So make sure there is a motive. Maybe there's a monster they need to beat, an item they need to retrieve, and NPC they need to talk to. Maybe there is a path of breadcrumbs. Maybe they need to accompany a weaker group, or see a specific site. If there is something important to be found on the journey, it can happen normally.....just be prepared for them ending it quickly if things turn south. Being side-tracked doesn't happen in high-level play unless there's a dang good reason they can't go on the normal track, or a dang good carrot on the end of the side-track.
Sacrifice: More Than Just Life Because of the survivability of high-level characters, the sacrifice of one's life for a noble cause is not that big of a sacrifice....it's significant, but it's not insurmountable as it would be in low magic or low level campaigns. Coming back to life is just a friendly church away (this is, of course, a tie and an NPC group that can be targeted later), so other things need to be sacrificed. Items are more important to high-level characters, and getting rid of them is tougher...but intangibles are much better. The 'nessecary evils' can be devestating.....having to kill a popular baron is an intense sacrifice of everything the character has faught for over his career, even if the baron is wicked and turning the townsfolk undead, and they don't know it. The death of a trusted NPC ally is more weighty than an adventurer's death, because it's never a garuntee that an NPC will want to come back from the dead. Having to cut off your role in the aristocracy because you disagree with the policies of the emperor is a grand sacrifice, though no one must die for it (yet).
Use the Resources: Certain spells and effects become significantly less potent when they *need* to be used rather than just *can* be used. The monsters are desgned with this very concept in mind -- golems in particular. If the PC's cannot solve the mystery *without* Divination; if they cannot rescue the princess *without* reviving the long-lost king and his armada, if they *need* to hop between planes to achieve their goals, these stop becomeing powers and start becoming plot devices. Think of the most "abusive" spells in the game, and then create situations that mandate them. Use these to drain the PC's of their most "dangerous" resources. Even high-level characters can only
plane shift so often before they run out. Whereas at low levels you may have nickel-and-dimed their food, at this level, you nickel-and-dime their first level spells. It's key in this to stop them from resting for too long....impose a time limit to keep spellcasters on their toes and none too potent.