Basically, after completing 26 levels, it comes. When it comes, run to the bottom fork and stand by the edge, and then fight like that, it's very fast.
The hidden hero is very powerful. After killing a few monsters, it will gain some strength.
I don't know why after passing level 26, level 27 doesn't appear. The recipe for the Wolf Tooth Dagger doesn't drop either. If you know, please let me know.
If you can't pass level 26, there will be many levels afterwards, and the hero's strength will keep increasing.