Is Conflux a broken castle?

I'm very curious how you manage to play with this Castle without upgrades of levels 1, 6, and 7. I read in one thread that the decisive battle takes place in week 4. But if the passage to another player is guarded by creatures of level 6, or even level 7, how do you defeat them? With magic? Or are you relying on Armageddon? But what if there are Ifrits there? An unupgraded Phoenix is easy prey!