Now THAT'S a Big Dragon! · published
These patch notes are full of spoilers for the Endless chapter, level 11 dungeon:
If you took the king’s gold in the level 11 dungeon instead of fighting him, you’re no longer stuck at dungeon level 10. You can return to the endless chapter dungeon at level 11, where the king has new dialogue and you can choose to confront him and start the king battle.
Existing saves that were capped after a bribe should pick this up the next time you enter the endless dungeon. If you're still stuck on level 10 after beating it once, sadly you'll have to clear the save game and try again. Chapters will remain unlocked after a Clear Save, though.