I just started reading this and thought the same, but also the fact that there's no way they are the only people in this place. People die all the time, so there's bound to be countless people inside that place. Probably the ones who attacked him are broken participants from ages past. So 900 years is an extremely low estimation if you ask meDue to the stated rules, it seems like one can cheese the competition just through patience. It appears like there are ten contestants, and the portal opens up every 100 years, so at worst, you're looking at waiting 900 years to get there, not accounting possible testing for the best routes.
Edit, forgot about possibility of turning into the mobsters during the wait, but we'll see.