After the first lecture ended, both students and teachers gave quite high evaluations of the class, and Professor Cronos was very happy, exclaiming 'Mamma Mia' several times, then sweating coldly behind his back.
He didn't understand anything that Professor Cobra taught.
In fact, until he actually traveled to a different dimension and faced "Crystal" together with Tenjo Hikari, he had little interest in dimension travel and was quite resistant to admitting the existence of "spirits".
Of course, after that, he gradually changed his mind about everything and also began to realize the errors in his previous beliefs.
However, as a duelist, what he prioritized in learning and research was not the things Professor Cobra taught, which made the contents of Professor Cobra's teachings particularly useful to him as well.
After all, no one in the world understands the Ancient Gear series better than he does.
As someone who had successfully negotiated and collaborated with the dimension of ancient machinery through personal capabilities and diplomacy, gaining many specialized cards from there, Professor Cronos had a very good relationship with the Mechanical Spirits.
So after listening to Professor Cobra's lecture, he reviewed and revisited it in his office for a long time, only then did he suddenly realize.
No wonder he felt like he was getting stronger lately, it wasn't an illusion.
Knock, knock, knock.
Someone knocked on the principal's office door.
"Come in."
The door automatically opened as Tenjo Hikari looked into the principal's office, bowed to Professor Cronos, and then asked, "Professor, did you want to see me?"
"Tenjo-san—" Cronos stood up to welcome Tenjo Hikari, gesturing for him to sit down.
Tenjo Hikari nodded, found a chair, and sat down casually.
After class ended, Professor Cronos had asked Tenjo Hikari to find him after all courses had finished this evening, seemingly having something urgent to say.
"What did you think of the two professors' courses today?" Professor Cronos asked.
"Very enlightening." Tenjo Hikari responded decisively.
In the morning course taught by Professor Cobra, he explained how to enhance one's spirit power, content that even Tenjo Hikari found very useful, taking copious notes.
In the afternoon, it was Professor Seraph's lecture on "Demonology."
On the surface, what seemed like "Demonology" involved demon summoning and fiend decks, but in truth, "Demonology" was a classic discipline from the Western Europe Branch.
Essentially, "Theology."
However, to avoid and bypass the Church's jurisdiction, Duel Academy simply called it "Demonology" for convenience.
The so-called Demonology doesn't teach students to recognize and understand these demons, but rather teaches students how to connect with these "extraordinary beings" and gain support from their power.
For instance, through ritual summoning of demons, monsters, or gods, then through contracts, gaining relevant power.
At first glance, it seems very evil.
But in fact, it's not like that at all.
Through the development and research of spirit power, this world has gradually mastered a special "Demon Summoning Technique," which, by following corresponding steps and methods, first sacrifices the appropriate materials, then summons an entity from another dimension using a certain card as a medium, subsequently engaging face-to-face with the spirit in conversation or even a duel, bypassing the "understanding" process mentioned by Professor Cobra, and ultimately gaining recognition directly.
The advantage of this method is that you can lock onto the power you desire, but the downside is that because it involves summoning the entity to this world, inherently the summoner is weaker than the summoned entity—in duels, regardless of winning or losing, the summoner provides the duel energy, and if there's insufficient energy, the spirit might dissolve into nothingness during the duel, returning to their dimension, even consuming all the sacrificial materials and duel energy.
This process is "irreversible."
Indeed—
This method requires the sacrifice of a "limit" during the ritual, and once the ritual fails, the summoner's spirit power will inexplicably diminish, unable to replenish through rest, only through renewed efforts to increase it.
And to let students more intuitively feel the power of this summoning art, Professor Seraph performed a summoning of an angel in class.
[Freya, Spirit of Victory]
This spirit was initially quite angry when summoned to this dimension, but after hearing Seraph's explanation and being told it could showcase for human cubs, it graciously began a duel performance.
Several students challenged it due to its "beauty," only to fail, and in the end, the guide said goodbye to the students before leaving as the time ended.
Many students were worried about Professor Seraph at that time, since according to his lecture, with the spirit's return to its dimension, the summoner's "spirit power limit" would certainly suffer a loss.
However, Seraph didn't react much to this; he just smiled and told the students that as a scholar, they must prepare and protect themselves before experimenting and experimenting, or they would end up needlessly losing some spirit power like he did.