The Gate of Life and Death exists to screen for Floor Masters. When the tower first opened, it's certain that not a single member of the Demon Race entered. So, how were Floor Masters chosen back then? The selection must have been made through the Gate of Life and Death. It's the most simple and brutal method.
'As for why no one at the Reincarnation Level has appeared,' Lin Xuan mused, 'it's probably not because the Demon Race lacks talent, but rather because once a Floor Master was in place, no one from the Demon Race bothered coming here anymore. There's no point unless you can successfully obtain a Reincarnation Level qualification. Even with that qualification, the most you can do is force a challenge against the Floor Master. You can't just become the Floor Master directly, which makes it all rather pointless.'
