Nasubi has been defined by one very dominant trait: he wants to do what is best for Kakin.
Nasubi would accept Halkenburg killing him, becoming king and install a democracy if that is what comes out on top in the Pot Ceremony.
Thus, the Burial Chamber is probably connected to that and part of creating a strong successor. If Nasubi wanted to keep ruling, he would not have started the pot ceremony (unless there is a reason inherent to the ceremony for it, like the Pot forcing him).
The machine cannot be an integral part to the ceremony, because the ceremony is probably older than technology.
In my opinion, we cannot exclude the possibility that it is a symbolic place. It keeps the corpses intact and after one prince won, his Nenbeast can devour all these bodies to become the legit king.