Decay, deadly poison, bones, corpses, souls, curses, blood, and mystery, are the eight major schools of the necromancer, and also the Eight Great Factions of the Necromancer Class. However, all these factions ultimately succumb to death, or rather, it could be said that the eight schools are all born from death itself.
All things lead to unity, and all things will ultimately return to death. This is the highest creed of the necromancers, and it also represents the state of the Eight Great Factions.
This is also why the ritual room is nonagonal, but there are only eight stone slabs on the Magic Circle, because the last slab, carved with the symbol of death, is right now beneath Jounouchi Hiromi's feet in the recess at the center of the Magic Circle.
This is the significance represented by this Magic Circle—all things lead to unity, and all will eventually return to death.
