The principle of immortality is unclear, and the setting collection related to "Tsuki-hime" only vaguely mentions it without explaining it in detail.
All we know is that Xiel is a descendant of Roya (he left behind descendants before he became a vampire), and the fact that Roya possessed his direct descendant caused an error in the world order, and it is an error that cannot be corrected. In layman's terms, it is a BUG.
This bug caused Xiel to be protected by the world itself, and the order would forever freeze her body at the moment when Roya awakened.
No matter what happened, no matter how her body was damaged, Order would restore her body to its state when it was frozen in a very short time.
As long as Roya, the source of the BUG, does not die, or the world order as the system itself does not collapse, Xiel will always remain in this state.
Will not grow, will not age, will not change, even more thorough than Scathach's eternity of being forever seventeen (thick fog), who will always be sixteen (this is true).
Of course, the world only gave Xiel unparalleled immortality. For ordinary people, it would be just that, so what if they can't be killed? An ant that can never be stepped on to death can't pose a threat to an elephant, and there is no shortage of elephants in this world. Dead Apostles, Servants, powerful magicians, and mysterious inheritors from all over the world can kill ordinary people like killing ants.
Taking the current Shinji as an example, he can easily kill hundreds, thousands, or even tens of thousands of ordinary people. Although it takes some effort, it is not too difficult.
Fortunately, Xiel's own qualities are excellent enough. Although she was born in an ordinary family, her potential is comparable to that of the first generation Roya. Because of Roya's possession, her potential was fully awakened, and then frozen by the world, which eventually became the foundation of her strength.
She has inhuman physical abilities and her magic power is one hundred times that of an ordinary magician. In terms of pure aptitude, she is the best in the contemporary world. The only one who can compare with her is Loreleija.
However, the difference in their magic skills is huge.
The gap is not due to background or environment, but entirely because Xier himself is resisting.
Human memory is a very strange thing, it is stored in the soul and engraved on the brain. Although Roya's awakening time is not long, his memory is engraved in Xier's brain.
Before becoming a vampire, Roja was an extremely powerful magician and the founder of the "Burying Agency". He was invited to the "Millennium City", the base camp of the True Ancestor, many times, which shows how powerful he is.
After becoming a vampire, he reincarnated eighteen times. Except for Xiel's generation, which was the sixteenth reincarnation—that was an accident. When the previous reincarnation died, there was no time to decide on the next reincarnation, so he was reincarnated into Xiel by mistake, which caused the bug to appear—and the unknown eighteenth time, each of the remaining generations of reincarnations was carefully selected. Those with bad family backgrounds and poor qualifications were not accepted, and those with non-human bloodlines were preferred.
During this long reincarnation of 800 years, Roya gained countless knowledge and secrets, which was comparable to the nearly 2,000 years of inheritance of Barthelmero. You know, knowledge inheritance can be lost, and magic imprints can also have problems, but Roya, who evolved into a higher-dimensional spirit with the power of Elquit, will not.
All this knowledge is stored in Xier's mind, and she can view it at will. After fully digesting this knowledge, Xier will never be inferior to Lorelaia. However, this knowledge is bound to the painful memory of destroying her hometown and slaughtering her family and friends. Looking through this memory is equivalent to reliving the past that is too painful to look back on.
Therefore, Xiel has always been resisting magic, and at most he occasionally performs small-scale spells of suggestion and adding special effects to the black keys for the convenience of the task.
This is also one of the reasons why Shinji did not use his Noble Phantasm and only planned to use firearms to deal with Xiel.
As for the other one, it is the armed form of the Seventh Holy Scripture.
As the holy light flowed, the holy book was freed from its ancient book form and transformed into an impact cone shaped like a heavy rifle.
The entire gun is over 1.5 meters tall, and the widest part of the "gun" is over 50 centimeters. The domineering shape, the silver-black metal shell that is darker than the dark blue monastic robe, the mechanical punk style, and the sudden change from the medieval classical hardcover book to the modern contrast give people a strong visual impact.
Yes, you read it right, this is the holy scripture that has been passed down by the church for thousands of years.
Of course, it was not designed to be this way from the beginning. The Seventh Holy Scripture was originally used as a tool for the final seal at the end of the ceremony because of its sacred symbolism, but later it began to be used as a weapon.
The original weapons were spears or stakes, but as time went on, they gradually incorporated the characteristics of modern weapons and changed their shape into spears and swords that were more convenient for actual combat. Up to this stage, there were still elements that reflected the majesty of the holy book.
The mechanical punk-style impact cone is a product of Xiel's magic modification according to his own preferences. In the previous life, when Xiel showed his weapon in the game, Shinji was really shocked. It felt like a Type 59 suddenly appeared on the battlefield of Mount & Blade. It was so sour and refreshing.
Now...
"Good weapon, I like it. I have something too, I'd like you to take a look at it."
While Shinji was admiring it, he took advantage of the time when the Seventh Holy Scripture had not yet stabilized to pull out two more domineering weapons from his backpack (coffin).
An RPG rocket launcher and a six-barreled Vulcan cannon. - Xiel was so frightened that he almost couldn't hold the handle of the impact cone, Kallen's eyes widened, and even Meilian showed a considerable degree of surprise.
The Vulcan cannon and RPG are actually not that bad. We have seen them before and have fought against modern weapons when performing missions.
From the fact that the "Seventh Holy Code" keeps pace with the times and constantly updates the form of weapons, it is not difficult to see that the Church is not like the Magic Association, and is not opposed to technological progress. There are even many agents who actively request semi-mechanized transformation to better complete the task of hunting heretics.
The problem is how to draw out the weapons. Everyone can see Shinji's backpack, it's just that big, it can barely hold a flamethrower, and it's not impossible to put some grenades and health packs in it, but how can these two weapons that are much longer than the backpack be drawn out
This is a purely technological weapon without any mystery attached. It is not a conceptual weapon and can ignore the laws of physics and change its form.
Could it be that the backpack was an extremely rare space item? How many weapons were hidden in that item
Shinji was obviously satisfied with the reaction of Xiel and others. The boy with the Vulcan Cannon in his left hand and the RPG in his right hand grinned and said:
"Come on, let's hurt each other!"
PS: Hiel's setting is "If she fights one-on-one with a Servant of average ability, a Noble Phantasm of Rank: B, and no special effects such as Fate Interference (the type of Noble Phantasm that only determines the outcome by power), she can only fight a defensive battle." But that is based on the premise that Hiel resists Roya's memory. If she completely digests Roya's memory, she will at least start as a first-class Servant, and it is not impossible for her to be a top-level Servant.
PS2: In the Fate line, Roja, who did not meet the princess, still completed the degraded version of reincarnation. After a certain reincarnation, he met Edmund (the Count) in his previous life. He used the knowledge of reincarnation to easily play the Count with his hands. If the Count had not awakened the secret treasure of Monte Cristo in time and realized the black flame that restrained the spirit, he would probably have died before he could take half of the revenge. Therefore, Xier is definitely a potential stock (if you don’t believe it, I will show you Roja’s ability later).