City Core

Info
It's a crystal-like with 20 sides shining blue light while floating. The City Core draws abundant magical power from The Source, it's an artifact that exist for the purpose of letting the person who becomes its master to make use of that vast magic power.

Even if it's said that this City Core is an artifact, it's unknown if the core is made by someone somewhere. There was a certain king who once asked the gods, but the answer never came.

The method to create one is already lost at the present time. Once, the Bornean sage, Trazayuya, attempted to recreate one, but he could only make a counterfeit with much lower performance at best.

The lord could establish this City Core to people so they could use it and uses ritual magic. Truly various magic; it could create walls that could defend against attack from high-ranking demon, attack magic that reduce armies to ashes, or climate magic that could manipulate weather.

Guards and viceroy are both representatives that lords have given authority to act on their behalves. They could borrow the power of the City Core, but the master is still the lord.

The holder of City Core, can appoint new nobles in behalf of the king.

[Nobles] are originally what people who control cities are called. The rank of nobles is indication of the level of authority a representative had. The one protecting the city is either baronet or a baron, the city's viceroy must be a viscount at least, those aren't just customs but in accordance to the authority level of the City Core.