So here are the general "categories" of high level things to consider:
Raw Powaa
This is just the raw amount of awesome the PCs can bring into your combats. A few ways to handle this:
Divinations
well used divinations can be very powerful and potentially adventure disrupting. A few things to consider:
Consider a series of high level adventures versus a "campaign". To me the biggest issue with high levels is the "campaign". Having 1-3 adventures at high levels with some world ending threat....sure its a ton of fun. Trying to do another 10-15 sessions....well now your having to up the ante all the time, and it makes world building a lot more difficult. High level is the endgame, there is no issue with just pushing the game till its natural end.
Raw Powaa
This is just the raw amount of awesome the PCs can bring into your combats. A few ways to handle this:
- Narratively: As mentioned before, its perfectly fine when a high level party encounters a mundane threat to just put the dice away and have everyone describe how utterly badass they are. For some players, this is actually way more enjoyable than the "real combats".
- More encounters: More attrition is generally needed at high levels.
- Time Limit: Probably one of the most important things to me at the high levels. You give a high level parties a week, almost nothing can stop them. A day, they are kicking butt. An hour....ok now things are interesting.
- BBEG is never shown until the end: The real BBEG should never be accessible until the very end. Either they are locked away in some planar vault (aka REALLY locked away), or the party doesn't even know who the actual BBEG is (though be wary of divinations in this respect), or they defeat the BBEG who then turns into the REAL BBEG (ala final fantasy style). If you do anything less than this, just expect your BBEG to get snipped along the way.
- The end place neither needs to be epic or mobile. If the adventure resolves around a static place, you are just opening up the door for epic shenanigans to ruin your day. So either the place needs to be suitable epic so that normal high level shenanigans would not work (like Asmodeus' palace or something), or it needs to be a place that can shifts or move around so the party can't just target it.
Divinations
well used divinations can be very powerful and potentially adventure disrupting. A few things to consider:
- Create a problem without a known solution: Part of the fun of DMing high level adventures is....you don't have to have everything worked out. Feel free to create puzzles that you don't know the answer to, in your head you go "I honestly don't know how to get into this thing" and then let the players flex their high level investigatory and divination skills to try and find solutions.
- Mysteries are the means, not the end. The classic murder mystery does not exist at high levels, its just too difficult. Instead, make that the B plot, a side thing that leads to the real adventure.
- If a divination doesn't work, have a good reason why. Spoiling a divination is fine once in a while to shake things up, but if your ham fisted with it, it will just deflate the party.
- Counter divination: What's good for the goose is good for the gander. If your party is using divinations to sniff out the BBEG, no reason they can't use the same. Feel free to create traps and scenarios specifically tailored to the weakness of one of your party.....as the BBEG of course has learned about their most important threats.
- Nothing is linear at high levels. Just throw away the linear dungeon at high levels, it doesn't work well. Instead go for a "need X things" approach. Example: A dungeon where you need 6 keys from 6 different rooms to open up the planar door (not a regular door, high level parties would smash that, has to be some crazy space door). Now make those 6 different rooms exist in 6 different planes. Now, make one of the door only exist in the past. Ok now we are talking!
- Move away from Space towards Time. Getting to the X place is no problem...but the party also must get there by X time. This combined with good time pressure can add a nice element, or it can slow the adventure down to allow for more proper pacing.
- Use Teleport blockers sparingly. Having an entire dungeon teleport proof is a bit meh....having one small room in a dungeon proofed can be a nice play.
Consider a series of high level adventures versus a "campaign". To me the biggest issue with high levels is the "campaign". Having 1-3 adventures at high levels with some world ending threat....sure its a ton of fun. Trying to do another 10-15 sessions....well now your having to up the ante all the time, and it makes world building a lot more difficult. High level is the endgame, there is no issue with just pushing the game till its natural end.