I think I got here by using the return exit after leaving the bonus level, after the timer ran out. With my savefile, the game crashes if I kill too many monsters before I exit again. Otherwise, it would be totally awesome and completely doable to actually be able to fight all the named monsters on one level.
By the way, I got most of my bravery points from killing moving walls and lava pits with wands of digging and other strong weapons. Digging and clearing lava are not exactly brave things to do.