So, if you don't reach the resurrection point, you will eventually be eaten by the "end-human" and respawn at the starting point. Restart your whole journey over again.
But if you are still alive but haven't reach to the resurrection point, you may turn into those "end-human" because the underworld is not the place meant for the humans in the first place. Stay too long and you become the very thing you are running away from at beginning.