The Perfect Balance

the perfect balance is a biome that only spawns when certain things are done in a certain order. depending on if the world is on pre-hardmode hardmode or war mode when defeating any boss will give you a "legendary quest" that when used will read text on the screen about what quest you must do

pre hardmode
to find balance slay the king of goo

and find the sword of cobalt blue

defeat the lord of all eyes

and feed the evil worm his demise / and show the king of brains his own demise

hardmode
to find balance slay the duo of terrible nights

and cure the curse of eternal fright

defeat the monster that shakes the ground

and stop the restlessness that grows underground

war mode
to find balance slay the golem of ancient time

and end the cult at the cursed shrine

defeat the pillers of endless moon

and seal the fate of certain doom