Beat Them At Their Own Game

The death rate at the first level of the royal mausoleum was always the highest. 

All those who entered the royal mausoleum were immediately attacked by Knife-throwing Ninjas. The ones who entered first would find that all firepower was concentrated on them, and they were usually the ones to die!

In the ten or so days since the royal mausoleum had been opened to the public, many people intentionally avoided being the first to enter the royal mausoleum and allowed some rash hotheads or people who believed themselves to be good to enter ahead of them. 

Those who entered first would basically all die. Almost no one survived it.