this is basically another boss rush. here's some tips:
- default boses in smbx have been overused to death; nobody likes fighting the same bosses over and over, with the only difference being custom graphics.
- what you should do instead is making a completely unique boss: you're going to need layers and events or learn lua to make unique bosses. i don't know how to do them, but i think this guide might be helpful:
viewtopic.php?f=35&t=6110
- alternatively you can still try using default bosses, but changing them enough so that fighting them feels like a new experience. if you want to do this, id recommend checking this:
viewtopic.php?f=81&t=8890