Before we get into how to challenge characters who can throw around spells like destruction, disintegrate, and power word: kill, let’s talk about what not to do. When your players come up with an interesting solution to whatever problem you’ve thrown at them, don’t try to figure out reasons why it shouldn’t work. Say “cool” and let them do it.

In fact, I recommend not having solutions to puzzles in mind. At this level the characters have access to fantastic abilities. Even the non-casters should have some interesting resources from magic items. Never underestimate the versatility of a rogue with ranks in Use Magic Device and a staff or wand. So give them grand obstacles and let the players figure out how to get past them. Don’t make things totally impossible. You should have a variety of possible solutions in mind. In fact, write a few tips for if the group gets stuck and calls on some form of divination for clues. Just don’t try to force a single solution on them. Let them enjoy outsmarting the villain’s traps with creative uses of their tools.

When my group tackled A Paladin in Hell there was a metal maelstrom blocking their path to a tower. It was in effect an epic, spherical blade barrier. The book’s solution was mostly to dimension door inside the center. That could have worked. My group flew above it with a summoned airship. They cast fly on themselves to cushion their fall. Then they created a sphere of iron around them and fell space marine drop ship style straight through the deadly swirl of metal and rocks. I let it work, because it was awesome.

Also don’t be afraid to throw in easy encounters. If a group of soldiers tries to stop them, realistically they shouldn’t be 15th level or something crazy. So let the party bluff their way past with ease. Or if there is a fight, hand wave it without any rolls. It’s ok if high level characters throw their weight around every once in a while. If they let the power go to their heads you can always send a paladin champion to have a talking with them later.

Bottom line is, if you try and run the same sorts of challenges that worked at low levels, you are going to frustrate yourself to no end. Embrace the fact that high level characters are up there with Hercules and other mythic figures. Look to super hero comics for inspiration if you have to. But above all, let the characters be awesome.