If not for the age cap, quite a few old monsters would've tried to go in.
Unfortunately, the rules were already firmly set. Though the Spirit Garden of the Planting Fairy had long since perished, the mark she left behind remained incomparably powerful.
Even immortals might not be able to break it—let alone those who had not yet attained immortality.
But in this age, cultivators who reached the Body Integration Stage before three hundred were rare exception among the elite disciples of major factions.
For ordinary cultivators or even gifted ones, trying to reach the Body Integration Stage before three hundred years of age was about as likely as reincarnating into a top-tier bloodline.
Moreover, cultivators below the Body Integration Stage entering the Immortal Fall faced an extremely high risk of death.
That's why the human side didn't intend to send too many people in. The devils, it seemed, had similar plans.