For advancement beyond 1st level, refer to the class feature pages.
The optional rules for Feats and Multiclassing are not used.
See 100 XP Advancement.
Story Mode is only intended for characters up to Level 10. (About 25 game sessions.)
When a character reaches Level 10, they may continue adventuring, but they no longer advance.
When the player decides the time is right, they provide an epilogue for their final days, then set off to the Land of Legends (or your world’s version of Valhalla, Undying Lands, etc.), never to return to the land of mortals.
This lets players reach an achievable and satisfying end for their character — i.e. a way to “win” in a way that is mythically inspired.
It also focuses the campaign on power levels that are easier for most DM's to provide interesting challenges for.