The timing of your post is so interesting! I just started back on Season 1 levels now that Return to Morlovia is over. And I’m stuck too, on 21-7, just two levels ahead of you.
Having just beat Advanced Morlovia (I took a victory lap here) I was shocked to get defeated so easily! Then I loaded up with Battle Items and tried again. Another loss!
Part of the problem is the fact that I don’t have a lot of strong yellow heroes and the Elite Enemies are purple.
But based on @Rude’s comment I guess the difficulty really ramps up in this province! So it’s back to grinding and trying to get to TC 20.
Good luck and thanks to the other posters.