I've got a gut feeling that Aeternitas (the imperial heir Lucas rejected as his student and also the most powerful magician recorded in history) is controlling Anastacius.
We all know that Anastacius started to to change gradually after he started a voice calling him. At first he is shown to love and somewhat pity his younger brother, but overtime the voice paired along with his mother's hysteric tendencies poisoned his mind, hence beginning his transition of a loving brother to someone who was overshadowed by his once 'helpless and pitiful' brother.
Anastacius was the legitimate as well as the prince recognized by the late emperor (Claude and Anastacius' father) to be the heir to the imperial throne, however as Claude started to gain control of his magic (in this case his mana) his inferiority to Claude grew. It was mentioned earlier that Claude's magic was far more superior then Anastacius, which was the biggest reason why he created Jeneatte to begin with.
(As mentioned in my previous comments) Jeneatte was a product of black magic. She wasn't born from love, rather as a curse/weapon to destroy Claude. Anastacius created Jeneatte because he wanted her magic to surpass his younger brother's. However, it was kept a secret from Jeneatte which is why she still believes that Claude and Athanasia are her family (though they technically right).
Anastacius' immense hatred towards Claude drove him to use Claude's fiancée to bring him pain. However, this very decision proved to be a catalyst for Claude as he finally cut his blood ties and over threw his 'tyrant' brother.
To me unlike Claude and Diana's relationship (which was built on pure love), Anastacius and Penelope's relationship was quite 'special'. Both used each other for their own benefits. While Penelope used Anastacius for influence and power, Athanacius used her as a way to inflict pain to his brother, and a prominent subject of an experiment. Hence, their relationship was a 'give and take' one, an act of pure selfishness which is ironic because unlike them their daughter tried her best to be anything but selfish. Though she desired a happy family, whenever she wanted to grasp onto Claude and Athy they slipped away.
This caused a major problem because due to the nature of her power Jeneatte's dark 'energy/magic/mana' grows as her desire and longing for a perfect family grows. Giving Anastacius a perfect chance to ruin his brother using Jeneatte as a middle ground to attack Claude and using her naivety against him.
Though naivety/innocence can prove to be rather helpful at certain times, Jeneatte's proved to be lethal. It made it easier to use her against others or even mold her at free wilL
I don't know if anyone else noticed or even if this was intentional or not but, the character of Anastacius' mother bears a uncanny resemblance to Penelope. Be it their similar design, using their children to gain power or even them losing their minds at some point. Personally, I found the similarities quite ironic.
Even if both her parents were nothing but selfish at the end, they didn't start off as pure evil as we see in Claude and Anastacius' past memories. At least not Anastacius, since he shown to be pretty similar to Jeneatte in the way that he was kind and welcoming. But along the way everything started to changed along the way as soon as he started hearing the 'voice' calling him.
His changes began as he would often try to follow the 'voice' and get lost in his own thoughts. The 'calls' soon turned into taunts as it mocked him because of his incompetence compared to Claude. He felt betrayed as his family looked at him with eyes filled with pity, because his younger brother (who had almost no right to the throne) began to grow powerful. He watched as his mother fell into despair as she realized that her dream for power (including her honor) began to crumble as Claude started getting getting recognition. His mother urged him to take the throne in order to restore 'her' pride that she lost when an illegitimate child was brought into the court. At the end of the day no matter how hysteric her actions became she was his 'mother'. Not only was it shocking for him to witness such a scene of utter desperation when he was young, he was surely caught in the middle of a dilemma to choose between his younger brother and mother.
Though this pity didn't last long enough for him, the 'voice' slowly started to take advantage of his inner conflict (just like how he took advantage of his daughter) slowly molding him to the person he is today. The voice manipulated his inferiority to turn what started as a brotherly love that was born from loathe into immeasurable loathe. Soon his hatred changed his personality to one of a twisted puppeteer. He orchestrated a plan to destroy Claude by playing others, while willfully letting the the speaker of the 'voice' control him.
I'd also say that even after all that Anastacius didn't lose his final touch of humanity when he didn't kill Diana altogether (knowing she was dying anyways) and his subtle acts of affection towards Jeneatte (though it has it's own hidden meaning).
Theory:
To come to why Aeternitas maybe the 'voice' Anastacius keeps hearing:
At some point, in the manhwa we saw that Aeternitas was brought to Lucas, so that he could be taught magic to which Lucas blatantly rejected since to him Aeternitas appeared to be dull and weak. Lucas even questioned his legitimacy as an heir due to his weak demeanor.
However, when Lucas went to 'sleep', Aeternitas proved Lucas' words to be wrong, as he soon grew to be the most powerful emperor who could wield magic.
But where did his magic come from?
What was the true nature of his powers?
Lucas being the all powerful magician who can sense the faintest trace of magic, how could he not know/sense his powers?
What if the use of black magic in the imperial family began with Aeternitas? What if Lucas' blatant insults hurt his pride to the point where he became desperate to be validated by the magician he looked up to so much that he seeked black magic to satiate his desire to be recognized?
Lucas who even acknowledged Claude's magic and legitimacy, how could he not sense Aeternitas' potential?
If you read through ch.78 you will notice how he was very shy to talk to Lucas (he was literally smiling in pure glee and blushing too) however observe how horrified/heart-broken he looked as soon as Lucas expressed his contempt.
We also know that Lucas went to sleep soon after that, thus Aeternitas never got to prove his worth to the one person he wanted to, the one who looked down at him.
Other then that it was also revealed that magicians live a very long life (Lucas himself being more than 200 years years old). On the other hand the name 'Aeternitas' means 'Eternity' (similar to the names given to the 'legitimate' heir of the imperial throne being 'immortal'). So what if...he found a way to live on? What if he found a way to keep his soul intact in order for him to reach his long-awaited goal?
Note that Lucas never met Anastacius since he was 'asleep' the whole time for as long as 200 years. How did Anastacius know the magic tower so well? And why did it seem like he was acquainted to him when he went to somewhat go through and destroy Lucas' things in his magic tower.
And lastly in the recent chapters it is shown that Anastacius constantly keeps losing control, which is when his glow in a hint of red/reflect a dull shade of blue and he begins to act like someone completely different.
So if the voice is actually Aeternitas why does he call Anastacius? Why does he keep manipulating him? What does he truly want? What does he gain from Claude's demise?
If my theory is true, I'd say the answer is Aeternitas sees himself in Anastacius. He projects his own past self and relates to Anastacius' despair.
If you observe you will notice the following similarities between them: Both were weak or at least believed to be so), both were heirs whose' legitimacy were questioned, both dealt with the consequences of being an apparent heir and finally both were mocked for their incompetence.
Maybe, just maybe what if didn't like seeing someone who had such an uncanny resemblance to his weaker that he couldn't bear the sight of whom who reminded him of his forgotten flaws/weaknesses. What if manipulating Anastacius was his own way of erasing the final fragment of his flaws to him?
[↑ Well it's possible that I'm reading too much into things but it's just a theory. However, I do believe Aeternitas' has an important part in all this since he wouldn't be mentioned for no reason at all. Other than that if the connection between Anastacius and Aternitas really exists it would ties everything down into a perfect cobweb of characters where everyone is some what connected to the other.]
All I wish for now is Athanasia and Claude's happiness, Lucas restoring Claude's memory, Jeneatte facing the truth, Roger and Ijekial's safety, Anastacius' redemption (yes, redemption and I mean it) and finally a happily ever after for Felix and Lily.
Is it too much to ask for? Maybe...yes? But I just want them to pursue happiness after everything they've gone through.
Roger don't die on uS-
AND CLAUDE DON'T YOU DARE LET ALL THAT PETTY MAGIC GET TO YOU-
WE.KNOW.THAT.YOU.ARE.STRONGER.THAN.THAT（/TДT)/
That was an amazing read
Something to note, the stronger her desire to be loved grows the more she is engulfed with dark aura (due to the nature nature of her birth + curse)
I'm pretty damn sure Juergen knows his Johanne's lil 'secret. Mah dude really been thinking he didn't catch the air of it (at least).
All i want is for all of them to be happy Leebin, Hwagok, Hwa, Seolhyun, Khakia, Ino, the babies and even the other vampires (Leebin's siblings). I lowkey want all of them to become vampires and live forever 'together' at least then vampires wouldn't have to live in solitude [alone] (;-;)
[Forgive me if I butchered the spellings-]
oml my dude rlly doesn't know what he's setting his sister up for (and himself too ofc) ٩(๑❛ᴗ❛๑)۶
man if the maids and everything in the 'palace' was a fragment of her imagination and nothing truly existed to begin with (and it was all a psychological reaction to help her cope with abandonment) -
THAT SHIZ REALLY GONN' HURT LIKE HELL
FFS SEUNGHO MAH BBY NAKYUM ALMOST GOT MURDERED AND UR AT IT MISUNDERSTANDING HIM-
GIVE HIM A BREAK HE IS TRAUMTISED (;-;) IF NOT ANYTHING HE NEEDS 'YOU' TO UNDERSTAND （/TДT)/
these misunderstandings.. but to him it looks like he ran away
GOD NOO PLEASE CLAUDE BE ALRIGHT (;-;)