I just finished a long solo campaign that went from level 13 to level 57. Let's see...
Until level 20, the campaign stayed within my homebrew campaign world. After that, the PC was introduced to Union. Once there, there was a merchant that had a problem with some epic critters (Invisible Stalkers with the Paragon template) in his house. The PC went there and cleared it, but also met some epic minotaurs that were burglarizing the house.
After that, the PC got hired by the Planar Cartography Society, as a search and rescue agent. His first mission was to go to an alternate material plane to rescue some surveyors that were out of touch. Long story short, he went and got them back (it lasted 3 game sessions and included different sites on that alternate material plane, but that's the gist of it).
After that, a fire elemental entity was causing some problems on the plane of fire. The Sultan of the City of Brass called on an old debt from the Planar Cartography Society to deal with it, which in turn asked the PC to take care of it.
Then the PC was invited to an elegant party in Union, where he met a noble epic dude flanked by two minotaurs. The same type of minotaurs that he previously met (plot expands). They got into a duel of snide comments, and that was that (for now).
Then the PC was called upon by a rogue that picked the enmity with an evil entity card in a Deck of Many Things, to deal with said entity in the Abyss. He went, killed it, came back, claimed reward.
Meanwhile, the PC's NPC sister is attacked in my homebrew. He goes there, kills 200 gargoyles, and finds her in a deep coma. It so happens that a very rare ingredient in some remote plane is necessary to save her (Wish and such just won't do it).
He goes, fights many critters, finds the ingredient, and comes back to save her. He eventually finds out that it's the epic noble dude from the party that ordered this attack.
He goes to the dude's material plane. Finds him, lots of battles in the dude's city and fortress, and finally slays him. I'm thinking about having someone true resurrect him later, but we never got to that.
Then, some aasimar of an elven deity requests his help into retreiving the deity's most important cleric (a 73rd level elf). The cleric has turned to evil against her will, and is under the control of a vassal of Grumsh, a chromatic dragon of great power, served by 43rd level fighter orcs.
He goes in the undergound place where it lives ( a huge cave complex with lakes and forests, and 2 dungeons), and wins the day.
Finally, I had some evil Advanced Elder Titan (CR 60) bluffing the over-gods into granting him godhood. He successfully prevented the four elemental planes from feeding all the Material Planes, and slowly but surely all creation is disappearing. The PC's deity appears (he's level 50 at that point), and asks the PC to go to deal with that (deities cannot access the place where the Titan is, only mortals).
And that was the final adventure of that epic campaign. He decided to retire with his love interest, becoming the ruler of the city where the campaign started.
HTH
I'm leaving it at that.
