For Marco, Mard Geer, who was currently reviving before his eyes, was clearly not as interesting as the matter of Erza's background.
"Still, maybe I should go back and call Mira over. These demons are all perfect for her. Every one of them can become one of her abilities."
Thinking of Erza, Marco naturally did not forget Mirajane.
After all, these demons were closely related to Mirajane by nature.
Simply killing all these demons outright would indeed be a bit of a waste.
It would be better to call Mirajane over so she could gain several new abilities all at once.
Buzz!
Marco raised his hand and directly sealed Mard Geer, who was still writhing with effort as he tried to revive himself, inside Crystal Wall.
A square Crystal Wall completely surrounded him from every direction.
"Don't be in such a hurry! I'll be back to collect you soon."
After finishing that, Marco directly activated Psychic Teleportation and left.
As a type of spatial ability, Psychic Teleportation differed from instant teleportation in that the former leaned more toward group movement, while the latter leaned more toward single-person movement.
The latter was more "instant," while the former had a greater range.
With the abilities and talents of the Jamir clan that came with the Aries Gold Cloth, together with the power of Marco's Cosmo, his Psychic Teleportation now covered a very wide area.
At the very least, he could move freely throughout all of Magnolia, far better than when he had encountered the Black Dragon before.
Buzz!
Marco's figure vanished.
In the next moment, he returned to the back courtyard of the Fairy Tail guildhall.
This was much faster than running. Even though Marco's current speed could reach several times the speed of sound, it was still definitely not as fast as using this ability.
As the light of the teleportation circle faded, Marco entered the guildhall directly and called over Mirajane and Gray.
Since he had already returned to the guild, he naturally could not bring only Mirajane with him.
He also had to bring Gray along and let the kid meet his father.
Under the current circumstances, Marco had not yet thought of a way to preserve Silver Fullbuster's life.
After all, Keyes was someone Marco absolutely had to kill.
Most importantly, that stubborn father might not necessarily want to continue clinging to life in this form either.
Silver Fullbuster himself strongly insisted that Keyes had to be killed.
In order to eliminate those demons, he was willing to die himself.
...
"Marco? What's wrong?"
Gray looked at Marco in confusion.
Clearly, there was no way he could imagine what he was about to face. That was far too difficult to guess.
"I have a surprise for you. Mmmm yep, it should count as a surprise."
Marco smiled as he spoke.
A Silver Fullbuster whose mind was still relatively clear, even if he appeared before Gray as a living corpse, would definitely count as a surprise for Gray.
At the very least, he could still meet his father and speak with him.
"A surprise?" Gray looked suspicious.
He glanced at Mirajane beside him.
"What about me?"
Mirajane looked adorably blank.
She wondered why she had been called along if this was supposed to be a surprise for Gray.
"There's a surprise for you too. Or rather, a gift. Some new abilities. I guarantee you'll be satisfied."
Marco winked at Mirajane, and she immediately understood what was going on.
"You caught another powerful demon?"
Mirajane had experience with this sort of thing now.
That previous Lullaby had been a "gift" Marco had given her.
Only Marco could give such a gift.
That was a demon from the Books of Zeref, after all. Of course, only she would accept such a gift too. If it were given to anyone else, they would not be able to use it at all.
"Not just one. Come with me. You'll know when we get there."
Marco smiled mysteriously, deliberately keeping part of it hidden.
He brought Gray and Mirajane to the back courtyard, then once again activated Psychic Teleportation.
Buzz!
Light flickered, and the three of them disappeared.
When they appeared again, they were already on Underworld Island, before the throne of Mard Geer, the King of the Underworld.
"Welcome to Tartaros's lair."
Facing the bewildered Gray and Mirajane, Marco introduced the place to them.
"What?! Tartaros?!"
Gray cried out in shock, clearly shaken.
Of course, he was not surprised that Marco could come and go freely inside Tartaros's lair.
What surprised him was that Marco had silently found Tartaros, that unimaginably mysterious guild!
"What happened?"
Mirajane looked at Marco curiously.
Hadn't Marco said he was going to Tenrou Island earlier?
How had he suddenly ended up in Tartaros's lair?
"They smelled Zeref's scent and came looking on their own. I happened to be on Tenrou Island, so I dealt with them while I was there." Marco spoke very casually, but his words made the corner of Gray's mouth twitch.
He was practically treating Tartaros like some random stray cat or dog by the roadside.
This was the most mysterious of the Three Great Dark Guilds of the Balam Alliance!
"There are definitely demons here, and they're very strong. This place is thick with the aura of demons. It's practically rushing straight at me."
Mirajane moved her nose slightly.
Demons were creatures she was far too familiar with.
She herself had demon factors inside her body. That was inevitable after years of taking over demons.
Of course, those demon factors did not affect her negatively.
They only improved her physical abilities somewhat.
"Tartaros is also known as Zeref's Bookshelf. Its members are basically all demons, demons created by Zeref."
Marco nodded and gave the two of them a brief introduction.
"That guy is a demon too, right?"
Hearing this, Gray pointed toward Mard Geer on the throne.
The King of the Underworld's body was currently condensing again, while the Demon Book radiated sinister energy and slowly transformed into a physical body.
"This is Tartaros's leader, Mard Geer, the King of the Underworld. Mirajane, this guy's power is very strong. He shouldn't be much weaker than Grandpa Makarov or Gildarts. Can you handle him?"
As Marco introduced Mard Geer, he looked toward Mirajane.
Take Over Magic was not something that could simply take over anything carelessly.
Just like when Elfman had tried to take over the Beast King before, if something went wrong during the Take Over, or if the target could not be controlled, the target might instead seize control.
"He's that powerful? As expected of Tartaros's Guild Master. In that case, I really do need to consider this carefully."
Mirajane was extremely surprised and stared wide-eyed at Marco.
After learning that this place was Tartaros's lair, she had expected the targets she might Take Over to be strong, but she had not expected them to be this strong, strong enough to compare to Master Makarov and Uncle Gildarts.
"He isn't Tartaros's Guild Master. He's only the one in charge. Their real Guild Master is someone else, and he's someone you absolutely wouldn't expect."
Marco smiled and corrected Mirajane's statement.
"Huh? Is it someone we know?"
Mirajane's eyes widened, and Gray also looked curious.
If it were someone they did not know, then of course they would not expect it.
Since Marco said it like this, that meant Tartaros's Guild Master had to be someone they knew.
"That's right. And someone you're both extremely familiar with."
Marco wore a mischievous smile.
Even after he had said it this clearly, Gray and Mirajane still could not figure out who it was.
Marco deliberately refused to say it right away, letting the two of them keep guessing.
"Who is it? Who is it?" Mirajane was extremely curious.
She leaned close to Marco and kept asking.
"All right, all right. I'll tell you."
Marco smiled and poked Mirajane's cheek, directly announcing the final answer.
"Their Guild Master is.... Natsu."
The moment Marco said this, Gray and Mirajane both fell silent.
They merely looked at him with strange expressions, as though saying, 'Do you think we're idiots?'
Clearly, neither of them believed it was true!
"You don't believe me? Then there's nothing I can do."
Marco spread his hands helplessly.
He had known no one would believe him even if he said it.
But the Saint System had already made it clear to him.
Something this important absolutely could not be false!
"You're not joking? How could Natsu be Tartaros's Guild Master?"
Gray did not believe it.
Natsu had grown up together with them since childhood.
When had that guy secretly gone out behind their backs to build Tartaros?
Besides, Tartaros had existed for a very long time.
It was the most mysterious Dark Guild. What connection could it possibly have with Natsu?
"Could it be... Natsu is also a demon? No, that's impossible..."
Mirajane thought of one possibility: that Natsu was a demon who had deliberately infiltrated Fairy Tail.
But with her in the guild, how could she not have noticed if Natsu was a demon? Her perception of demons was extremely strong.
"Natsu is indeed a demon, and his true body is right here with me. As for what exactly is going on, I can't confirm it yet. I estimate that Natsu himself probably doesn't know either."
Marco took out the Book of E.N.D. and indicated to Gray and Mirajane that this was Natsu's true body.
Then he dispelled their worries.
That kid Natsu knew absolutely nothing about any of this.
Marco could be one hundred percent certain of that.
He had long since checked Natsu's cards, and there was no problem with them.
Besides, the Saint System had helped him confirm Natsu's status as part of the protagonist group more than once.
Most importantly, with Natsu's brain and personality, he really did not seem like someone capable of acting.
"This..."
Mirajane was speechless for a moment.
This news was truly too shocking.
Gray let out a breath of relief in his heart.
He really did not want Natsu to be an enemy. He really did not want everything from the past to have been an enemy's disguise!
The two of them fought and messed around constantly, and though they looked like sworn enemies, they were also the closest of friends and brothers.
Gray did not want any of that to be fake. He did not want Natsu to truly stand against Fairy Tail.
Because if that happened, Marco would really beat him to death!
"Although this incomparably precious gift can't be Taken Over for now, hearing this news means I didn't come for nothing."
After recovering from her shock, Mirajane could not help sighing.
"No hurry. These guys can't stir up trouble anymore anyway. If Taking him Over is difficult, we can leave him here for now and go look at the other demons first."
Marco smiled and shook his head.
This was not the only gift.