Mark of Twelve

I understand now, I understand why the stories are told (Cain Luck upon witnessing the Third Mark being used,) The Mark of Twelve (十二の印) are twelve different Summoning Magics that's passed on within the Britannian dynasty. It gives the caster the opportunity to summon one of the Gods of Twelve, the twelve deities wroshipped on Eurasia. Unlike the Yakuma Eighteen Battle Gods Magic that requires a incantation or some sacrifice, the user of the Mark of Twelve is unable to summon the Twelve Gods at will, and can only be summoned if the god believes they must intervene. This means the caster has the possibility to summon any random god regardless of the condition, with the only condition if the god wishes to be summoned.

According to Ambrosius Aurelianus, he believes the Mark of Twelve is superior to the Yakuma Eighteen Battle Gods Magic due to its nature. The caster must go through fatal trial and effort to gain the Mark required to summon the god into the physical world, and only those of the Britannian dynasty do these which are known as the Twelve Labours.