Duke, as a traveler and an engineering equipment professional, systematically explained to over ten thousand people the nature, essence, and characteristics of fire using his knowledge.
For the magic apprentices of the Azeroth world, this was an almost entirely new theoretical system that didn't conflict with the magic knowledge they had previously learned.
They were utterly fascinated by his explanations.
Some formal mages wanted to find faults in Duke's theories to refute him, but they couldn't find anything wrong with his words.
Simple and easy-to-understand statements like "Heat flows from high temperature to low temperature, such as fire with high temperature can heat cold water," gained a new depth after being explained through professional thermodynamics theory. Even magic apprentices realized that their [Fireball] spell would undoubtedly improve.
Don't underestimate the Fireball spell. As the first damaging spell learned by most magic apprentices, the popularity of the Fireball spell is nearly 100%.
It's no exaggeration to say that the thermodynamics theory brought by Duke had a noticeable effect on improving the overall magic level of Dalaran.
Just as the last grain of sand fell in the magical hourglass used for timing, and the pleasant humming sound rang out on the podium, Duke precisely said, "That's it for today's lesson, my lecture is over." His timing was so accurate that it didn't seem like a young man, but rather the most experienced instructor.
For a moment, the entire hall was in an uproar.
"Instructor Marcus! Don't stop so soon! Tell us more! More!"
"We want to listen more!"
"Instructor, you're amazing!"
After a brief commotion, everyone seemed to realize that Duke wouldn't prolong the class. Immediately, thunderous applause filled the large auditorium.
The continuous applause was like a relentless tsunami, never ceasing.
Aside from the few unfortunate souls who had been injured and left earlier, every magic apprentice, every formal mage present, and of course, Kael'thas, all stood up to give Duke their sincerest applause.
As the applause subsided, Kael'thas was already on stage, a radiant smile on his face.
"That was incredible, Duke. Your lecture exceeded the limits of my imagination. I thought your strongest point was in practical combat, but I never expected your theoretical knowledge to be just as astonishing. I can't even tell if you're more of a combat specialist or an academic," said Kael'thas. Although he wanted to ask if these theories came from Medivh's Karazhan library, asking now would undoubtedly incite conflict. Kael'thas was simply happy for Duke.
Meanwhile, Jaina had become a star-chaser, admiring and questioning Duke enthusiastically.
"Brother Marcus, do you accept apprentices? How about I become your disciple?"
Without much cunning, the current Jaina was still a relatively innocent young girl. Her pair of watery blue eyes could easily make someone feel compassion and agree on the spot.
"Aren't you an admirer of Antonidas?" Duke blurted out.
"Eh, how did you know?"
Duke realized he had let slip, but it was easy to fix: "Who in Dalaran doesn't admire Master Antonidas?"
"Well, that's true. But the Master is busy, and he's said to be injured recently. Everyone knows he's actually in the laboratory every day."
A flock of imaginary crows flew over Duke's head: Antonidas, could you be more professional in faking your injury? Even a 12-year-old girl knows you're faking it.
Duke had no interest in meddling with Jaina Proudmoore. Ignoring her wavering personality between war and peace, he simply lacked the confidence to teach her properly.
Duke knew his own limitations. He wasn't a pure academic, and his understanding of the true magical theories of this world was limited. Even if he didn't like the Jaina from 'history' who had killed her father, at the very least, she was a capable hero in the Alliance's history and would play a central role in many future events.
Changing Jaina's growth could make the future even more unpredictable.
Duke grandly declined.
"I'm sorry, Lady Proudmoore. I'm actually quite busy. My main purpose in coming here was to visit Archmage Antonidas and help the Kingdom of Stormwind recruit some mages to rebuild the Royal Stormwind Mage Corps." At this point, many people were listening, and they suddenly understood.
Duke didn't hide his intentions. In the world of mages, equivalent exchange was the rule, and deception was frowned upon.
Duke smiled and turned to Jandice, "My assistant, you'll handle the inquiries about me taking on apprentices. Those who become my disciples or assistants will receive free guidance and access to the bottom three floors of the Karazhan Library. In return, they'll join the Royal Stormwind Mage Corps as my disciples, fighting for the Alliance and the Kingdom of Stormwind for three years."
Joining the Dalaran Mage Corps offered various benefits, and Duke's recruitment was similarly transparent.
It was both a risk and an opportunity.
Upon hearing the obligation to participate in the war, Jaina knew she had no chance. Her father would not allow her, still a minor, to get involved in the war. In fact, Daelin had already informed her that if Dalaran were in danger, a special mage corps would send her back to Kul Tiras as quickly as possible through teleportation or other means.
"Alas!" Jaina sighed, "It seems I can only wait until the war is over for a chance to visit Brother Marcus."
Duke just smiled and remained silent.
After the lecture, Duke was immediately caught by Antonidas.
Once again in Antonidas's laboratory, the white-haired and bearded old man didn't look so friendly anymore.
"Yo, Duke, this is not fair play. You're weakening Dalaran's potential for war."
Duke shrugged, knowing that although Dalaran had always pursued a policy of freedom, foreign dignitaries could freely hire any apprentice or official mage who hadn't signed a contract. But that was during peacetime.
Now, it was the interval between the Alliance and Horde wars. Dalaran had its own considerations. Duke's blatant recruitment wouldn't cause any overt issues, but the Kirin Tor Council might cause trouble for the Alliance later.
Duke bowed deeply, "For Dalaran's future and war potential, I am willing to make 1,000 copies of Karazhan's unique magic books and present them to the Dalaran Library."
Antonidas raised his long white eyebrows, "Mage, for 300 apprentices."
"Mage, 1,000 apprentices."
"Why not just rob them?!" The Kirin Tor Council leader glared with a raised beard.
"Wrong, this is better than robbing." Duke knew the importance of those unique magic books, and he wasn't worried that Antonidas wouldn't bite.
Knowledge is power!
"No way! That's too many, at most 500 apprentices."
So, the two important figures in the Alliance, who could shake the ground with a stomp, haggled like housewives at a market in this private laboratory.
The final deal was reached: 3,000 copied volumes of unique magic books in exchange for 200 official mages and 500 apprentices transferring over.