Idea #2 is "Justice League Greyhawk" - Looking at 4E, Epic level characters have amazing powers and are very hard to kill. Maybe we need to stop looking at dungeon crawls and start looking at other genres for inspiration - especially other genres that feature high-powered characters....like Superhero comics, movies, and games! If Heroic Tier corresponds to street level super heroics, and Paragon is similar to something like the X-Men, the Epic means you're one of the heavy hitters.What's more Epic than saving the world? Some staples of superhero campaigns that translate fairly well are:
- Alien invasions! So, instead of aliens use demons, or elementals, or dragons. Maybe Elemental Lords have decided to destroy the material plane to return it to the elemental chaos. Maybe the demons have breached an ancient gate and are pouring out of it en masse. Maybe Dragons have been rare in your game before but now they start showing up in flocks like birds - where are they coming from and why?
- Defeating the evil megalomaniac mastermind .is a pretty common thing in super stories too. What if an evil god has had enough of "balance" and finds an artifact or spell or forms an alliance that gives him the power to lock away the other gods? By level 20 or so Divine PC's would be fairly big players in the gods' organization on the plane - they might get one last urgent message hinting at what is happening followed by silence. When things start to change they will take action. When's the last time your 20th level cleric was on the run from something, hunted by enemies who know what he can do and want to hurt him? If you're hurting for plot think "what would Lex Luthor do? What would Doctor Doom do? What would Apocalypse or Darkesied do? The ideas should come soon enough.
- The War in Heaven - In some comics two alien races may go to war and that war eventually spills over into earth. This works a little differently than the invasion plot (or it could be used as a precursor to the invasion plot) in that the aliens are not interested in controlling the planet - it just makes for a convenient battleground. The PC's will probably not like random battles between an Earth Titan and a Pit Fiend wrecking their home town, especially if they are running things. They may start off like a fire brigade and try to stomp out individual threats, eventually realizing that that's not a long term solution. Instead they have to try and end a conflict between two alien races - and that's a whole different kind of problem than "Kill Orcus". Think of the ways this could be accomplished: 1) Try to arrange direct negotiations between the leaders of both sides 2) pick the side they favor then help them eliminate the other one, with the PC's as valued allies and captains among the force 3) Create an alliance of other parties (maybe other powerful characters or even some other outside race that hates both of the warring races) and wipe out both sides, or devastate them to the point they stop fighting. This allows for the possibility the new allies go too far and begin exterminating the now-weakened warring factions which ends up forcing the PC's the switch sides to maintain some kind of balance. Your aliens here could be demons, devils, elementals, dragons, giants, slaad, or some kind of undead.
- Sometime in the Heroic levels your party is hassled by demonic cultists and their annoying high priest (a recurring enemy) and eventually tracks them down and wipes out a temple to Demogorgon.
- In Paragon play a new powerful force arises on the fringes of their home territory and it turns out it's led by one of the 12 Death Knights of Demogorgon. Skirmishes ensue until the final confrontation with the army and its leader at the climax of the paragon levels. Maybe in one battle their old enemy turns up having been recovered and raised or maybe he's a demon now and leads one of the fights against the group. At this point the PC's may wonder why a demon prince is taking such interest in their homeland - a stealthy approach back in Heroic and now a more direct approach in Paragon. Maybe there's a resource or an artifact the prince is after? Or maybe he's secretly after on of the PC's and trying to lure him into a fall?
- In Epic the demons start popping up, and causing trouble, maybe kidnapping an important NPC ( a love interest, an apprentice, an heir), forcing the characters to pursue to the Elemental Chaos and eventually to the Abyss. The party must fight through a horde of demons before facing off with the big bad himself. If you just want to have a big fight, let the party face off with the remaining 11 Death Knights of Demogorgon first, before the big bad enters the field. At this point you could go for a straight up fight or maybe there's a twist - the prince doesn't want to fight the PC's, he wants their help in defeating some other evil that's too strong for him while he's holding off his rivals. Tharizdun, elemental lords, a titan - there's something else out there that he can't beat so he's looking for help the only way a demon can. There are all kinds of possibilities here with the party having to decide if they want to help a demon prince out, whether to take him out first, or if he's even telling the truth.
One of the challenges at Epic is filling out 10 levels worth of action. One of my solutions if you are going to feature a Big Bad or Bads is to make the lieutenants interesting (and powerful) so that it makes their leader that much more impressive. Maybe the deathknight Vorthax is known for having a skeletal appearance, wearing burned and blackened plate armor, and wielding a greatsword that burns with green fire.His powers use a lot of fire and he mostly fights with his personal Nightmare and a pair of corrupted fire elementals. A different knight might have blue skin and live in a fortress in the frozen north, having a lot of cold powers and fighting with n army of undead. The others would have their own quirks and flavor and be of varying power levels. Think "Supervillains" here if you run out of easy ideas, it could restart the creative engine.
In the example above you could detail out each of the 12 Knights and have the newest and weakest member be the climactic opponent for Heroic tier, the one they face in the final battle that takes them to 11th level and sets them on their path for Paragon. A rationale here could be that rather than living in the Abyss each knight has to build and maintain a fortress on the material plane and that's what this one was trying to do when the PC's stopped him.
During the Paragon adventures there could be several quests involving contact or conflict with the Knights until at Epic levels the group realizes they are the key to defeating Demogorgon and targets them systematically. They wouldn't be the focus of the campaign until early Epic, but they lend both continuity to the campaign and a sense of accomplishment as these long-term evils of the campaign world are slowly extinguished The characters become mighty heroes righting wrongs and establishing themselves as the defenders of the world, then face off with a major threat - the master of these immortal terrors himself. At that point it could be a straight-up fight or the DM could throw in some twists as outlined above.
Overall I think it's a valid approach to running Epic adventures. It could begin as a more reactive approach to things - superheroes tend to be more reactive than proactive anyway - but it doesn't have to stay that way for long. Once the threat to the city/kingdom/world has been identified then they can go on the attack to resolve it, hopefully leading to a satisfying ending to the campaign.