Suddenly, that light. The Chalice and the Sword, #1

It was the year 797 and Charlemagne's reign was about to reach its peak. The monarch's sword became the guarantor of the stability of the Church in terms of secular power, but also of its expansion at the level of spiritual domination in Europe. Soon after, Pope Leo III crowned him Emperor of the West. However, in an abbey in Germany, a fabulous object is kept, protected by the greatest secrecy, which, it is said, gives unlimited power to the King; but which, for this very reason, arouses in its enemies an immoderate desire for possession.
At the death of the nonagenarian Ramiro, a disciple of the monk who had taken it out of Spain to prevent it from falling into the hands of the Muslims and whose reputation as an all-powerful magician had made him his formidable guardian, there was a cruel struggle in the abbey among the various groups of spies in the pay of the great powers of the time to seize it or,  at least, to use it for their own benefit.
To do this, they will not hesitate to murder and torture. But when they finally manage to find themselves in front of the coveted object, they systematically die, because they do not know the key that would have allowed them to use it correctly. Bernardo, a young novice who has recently arrived at the monastery, will eventually discover her.