Los círculos mágicos...
At a very basic level, We could define the magic circles as a ring of runes within the body itself; therefore, the fundamental element to be able to constitute it was to have access to the energy of the will; luckily, at the moment, something is within the reach of the majority. Of players.
For its maintenance, there was a mana cost that would be extracted directly from the magician's mana cores; this in itself was a limit, since you could never have a circle of a level higher than the subject's own ability to regenerate mana. , although raising the maintenance cost to a level that is too demanding would be counterproductive, since it would be impossible to feed the circle's own reserves and would make it a burden for the magician.