Basically, a party or you alone goes in to a room, and one boss is spawned at a time, starting with, say, mano. And ending with maybe Chaos HT or PB.
Each boss defeated earns points, these points could be spent on things such as: (suggestions, the GMs could feel free to add or take away any) Equips, NX, pink scrolls, chaos scrolls, white scrolls, mesos, etc.
It'd also make a fun way to train at higher levels.