mamba
Legend
Vecna, the one adventure that did go to 20, Acererak ends at level 11, Strahd at 10, Demogorgon and Tiamat at 15Vecna: Eve of Ruin.
...Acererak, Strahd, Demogorgon, Tiamat,
...Tasha, Fizban
So they barely have to tune them down for a level 10 adventure
Also, you talked about marketing, which is what I referred to when I said I do not see them
fighting tough monsters (for that level) is something you can do at any level, arguably even moreso at lower levelsI don't have a problem with 'weaker' Demon Princes - I loved AD&D. But the key there was the mortal levels scaled indefinitely (even if the benefits of leveling were largely halted at 10th) to give the illusion of super heroism.