This post is translated from the original post written by baidu user白龙圣骑士SK
Apparently I’m not the only one obsessed with Zoro-Agruga.
I. Location: Heimdallr
II. Time: 10 years after the death of Dreichels, 50 years after the War of the Lions’ End.
III. Cause: Corrupted by the Holy Beast of Earth. The dragon [Zoro-Agruga] links the spirit of man to chains in order to increase the [Noct Familia] kinship. 200 years ago, the ones who became vampires by touching the remaining miasma reached the point where they’d cause an uproar.
The dark dragon fought in Chapter 4 of Sen III is nothing more than that “kinship”, sure, it is a strong cryptid, but it should be nothing for the combined forces of the witches and the gnomes.
IV. Symptoms: Those affected by the miasma exhibit symptoms including acting on instinct, losing self-awareness, strong combat abilities, and suddenly disappearing (because they can walk the spirit path).
According to Celine, those vampires who appeared 200 years ago possessed strength far beyond normal people, and had the ability to walk the spirit path.
V. Dark Dragon Revival Incident: The entire process of becoming a “vampire” is shown in Sen III. 
The location above is in the underground cemetery below the Imperial Museum. The red pleroma grass began to appear, which was the sign of the Dark Dragon’s mausoleum before the spatial distortion appeared.
The pleroma grass began to glow and then the Immortal Kings appeared. These monsters are encountered later inside the Dragon’s mausoleum, so they are linked.
Headmaster Aurelia and Randy describe them as attacking without a word, and then suddenly disappearing.
Emma says that they “belonged” to the kinship.
It can be seen from this that the situation 200 years ago and the events this time are very similar, and the main difference seems to be the extent to which the dark dragon was revived.
The point I am trying to make is that 200 years ago, the dragon was at least in a semi-dead state, and was finally destroyed by Roselia, and the vampire incident was calmed down.
“But what evidence is there to suggest the Dark Dragon was revived?”
One of the reasons is that in “Red Moon Rose”, a male human and Roselia walked through the sewers into the Cemetery to destroy the Elder Vampire who was controlling the “kin”.
There are several underground tombs in Hemidallr, one is underneath the park, and houses the bones of the Dark Dragon.
The other is seen in Sen III, and was directly changed into the Mausoleum of the Dark Dragon.
The pattern on the ground and wall in both tombs is the same, and even seems to display the likeness of Zoro-Agruga.
It can be inferred from these designs that the underground tomb was built specifically for the Dark Dragon.
The “elder vampire” described as the culprit in Red Moon Rose was not a normal human, but was the Dark Dragon itself.
Another reason is that when Roselia appeared in the spatially distorted tomb, she was not surprised to say that beyond the door was the Dark Dragon’s mausoleum, apparently she had seen it in the past.
VI: Reason for the Revival 200 years ago: The explanation given by Roselia as to why the Dark Dragon revived in the current time is that when a large amount of spiritual power (curse) is gathered and concentrated in the cursed land, the Dragon regains its flesh.
The question is, if strong spiritual power was what revives the dragon, why did it not occur immediately after the War of the Lions, but instead 10 years after the death of Dreichels?
As stated in the Black Records, during his later years, the emperor was enduring the onslaught of the curse alone. It can be understood that the needed amount of curse to resurrect the Dark Dragon was being suppressed by the emperor for 40 years.
Before his death, the emperor thought:
(the way I lived my life is not in vain, just as long as the Goddess came to greet me before “it”.)
In short, when the emperor died, he ceased holding back the curse, and it was released back into the land, at this time, there are still 10 years before the vampire incident.
In the novel “Red Moon Rose”, the first vampire appeared 10 years before the incident.
Thus it can be inferred that after Dreichels died and released the curse, the Dark Dragon was revived, and it took 10 years for it’s curse to become widespread.
VII. The “True Ancestor”:
Now we know that the series of events 200 years ago was triggered by a series of “effects” rather than an actual vampire.
The “Real Vampire” (the only one who does not die) is only one person, Roselia.
According to Kurt, there are many legends of witches and vampires in the forest of Isthmia.
However, Roselia said that only she is special, and the rest of the witches are ordinary people.
When Roselia speaks about her birth, she was not born due to normal reproduction, but was born because the previous elder died.
This suggests that only one true ancestor exists at a time.