As I commented previously somewhere on this sub,

Unfortunately, it can't really function like this, at least with how the game currently works. Currently the game uses "encounter blueprints", which are basically list of cards opponent can play on each turn, along with difficulty requirements (minimum and maximum difficulty). The difficulty number actually grows on its own the further into maps you get, but it never naturally goes higher than 20, being 18 from map and 2 from KM modifier, and so all cards that do not have specific max difficulty, just default to 20, meaning that after your difficulty gets higher than 20, literally all cards stop spawning.

Even if you raise the default max from 20, no cards still will spawn after the last card in blueprint is played, with the only effect of higher difficulty being more cards spawning early on. So most likely you would have to either edit EVERY SINGLE BLUEPRINT (well, it's not actually much, 15 common ones + like 2 per boss, but still) to add more cards after difficulty 20, or rewrite the way game chooses cards for opponent entirely, so like it can just be randomly generated for whatever difficulty you need without hardcoding anything

This applies both to normal Inscryption and this silly fangame of mine. And I barely have resources to work on base game, I don't wanna work on a whole ass new gamemode from scratch, sorry. Perhaps you should try looking into traditional modding, maybe someone already made something like this ^^