So this is the home of the genie.

　I look at the demon's hideout from the top of the cliff.
　It was the ruins of a fortress built in a large canyon.

　I followed the reactions of the markers attached to the monsters and came to their hideout.

　At first, I was going to use transition magic to simply go and eradicate them, but I didn't know what kind of place there was and how many demons were there, so I used flight magic.

　If the destination is an urban area and there are a lot of evildoers, there is a big risk of an immediate battle and the townspeople will be killed.
　And if you use transference magic, even if you use a magic that hides your appearance, the dimensional distortions will be seen and the invasion will be exposed.

　I don't want to get caught up in the dark workings of evildoers, for goodness sake.
　That's why I want to round up all the demons if I can.

　It's not too far away from the town where the marker stopped responding.
　At most, it was only a few hours away with flight magic.

　We used our exploration magic to confirm that there were dozens of life signs moving around in the fortress.
　It's still suspicious that someone is still there, even though I'm sure it was decayed and destroyed.

''But a fortress built on the bottom of a ravine in a strange place.

　It seems that this fortress has not been used for a long time, and it looks tattered.
　However, even so, it seems that at least a minimum amount of preservation magic has been cast on it, so it looks like it could be used if it were cared for.

It's not just a matter of time before you find yourself in the same situation. It looks like it's broken, is it a relic from the same era?

　Oh, come to think of it, the laboratory built in the cave the other day was a secret facility for defeating a magical beast called the White Woe, and this fortress may have been built on the bottom of the valley for that purpose as well.

''Then shall we go?''

　I, who had already activated the magic of concealment, headed unabashedly towards the ruined fortress.

　◆

I knew I'd recognize that structure.

　Even as I proceeded inside the fortress, I felt nostalgic for its architecture and interior.
　During my heroic days, I used to be sent to these kinds of fortresses to fight monsters and demons.

　If you were a good commander, it would be easy to work together with the army and fight, but if you were concerned about your rank and honor, you wouldn't let them fight you, and the damage would increase, so it was difficult.

　And in order to protect the knights and soldiers who were being dealt with, I made a range magic such as High Area Heal to cover them even if they didn't have permission to go into battle, and secretly covered them from inside the base.

'Oops.'

　When I was nostalgic for the base in the fortress, I heard footsteps approaching from ahead.
　Of course, the presence isn't a person.

　It's a pair of witches.
　It's probably a patrol inside the fortress.
　They are coming towards you while making boredom-stricken small talk.

I'm sure you've heard that? Are you saying that the people who went to attack the Dragon Emperor were wiped out?

Huh? What's that? A failure with an army that large?

　Oh, you mean the demons who attacked the town.

"Apparently, they were beaten back by the Dragon King alone.

Unbelievable... A dragon emperor is so strong.

I'm sure the top brass are wary of the possibility that the dragon knights are reviving in secret because the golden dragon has followed the dragon emperor. I'm sure they think that this case is also to lure us out by daring to expose the Golden Dragon's existence.

Do you think we're the ones who got lured in?

There's a good chance of that. The story goes that the Dragon Knights have been rebuilt and that they've conducted a massive field training exercise to lure us out.

　Well, I don't remember thinking about that.
　If anything, I just hurriedly got ready to intercept them.

'In fact, the town's warband was apparently equipped with simple weapons made from dragon materials.

Why is it so simple?

They say that for all its poor looks, it performed unusually well.

　Huh? I don't remember having to make that kind of a setup, okay?
　That was just spare equipment for the people who were in the process of maintaining their equipment.

'I see, it's obviously a disguise.

Yeah, they put on a poorly equipped outfit to fool us and get us all out of there.

　Well, that's a lot to take in but wait, no?
　Maybe that's what it was all about?

　That's really what the guild asked you to do, isn't it?
　The town had equipment that was disguised as the real deal, and in order to give it credibility, they asked me to get a number of them, I think.

　I see, that makes sense to me!
　The reason why the adventurers were raving about the equipment they made in a hurry was also because those people were actually the disguise of the soldiers of the garrison guarding the town wearing the equipment they were really meant to wear.

　As expected of the Dragon Kingdom's Dragononia garrison.
　Even though the Dragon Knight was gone, they were still making preparations against the foreign enemy.
　Yeah, even if the Dragon Emperor is gone, his intentions are still intact.

　As I was thinking about this, the demons who were making small talk passed by me.

Well, I guess I'll have to check out the fortress, too.

　The fortress is already decaying, so I don't think there's no need to worry about getting humans involved, but if there are hostages kidnapped from somewhere, it's a bad idea.

　Besides, there might be a transfer gate that can be moved to the demons' headquarters.
　If they find that, we should make sure to damage it so that we humans can't touch it for a while.

　So, I'm going to walk around inside the fortress.
　I'm not sure how many people are inside the fortress, and I'm able to determine whether they are human or not with the help of exploration magic.
　But it's definitely necessary to check with your own eyes just in case.

''Even so, the demons love to use our ruins,''

　I don't know if it's a hassle to build new, but you could take the rent for good.

Oh...

　The word "rent" gives me an idea.

'Yeah, that's a good one.'

　Once that's decided, we'll start acting immediately.
　Fortunately, the structure of this fortress is not much different from the common fortresses of the previous life.

'Maybe it's over here......ah, there it is.

　It didn't take long to reach the place you wanted.
　Since the place is a place, the exploration magic doesn't even respond to the demon's response.

　It was a large room, with a huge sphere on top of a thin pillar in the center, and a number of thin pillars extended from the sphere to various parts of the room.

　And the true nature of this round sphere, it is a magic power reactor.
　Just as the word says, it's a power source that runs on magic power.

　In the past, in order to fight against powerful mages and giant monsters, they needed a power source to move the defensive magic items installed in the fortress.
　Human magic power alone couldn't run the defense equipment all the time.

''Yeah, this should work if we can fix it.

　The fortress decayed a long time ago, but the inside isn't too damaged, as the state maintenance magic seemed to have been in effect until recently.
　This area is the heart of the fortress, so they must have put more effort into its preservation than the outside.

''Then shall we begin the repairs?''

　Just to be sure, I put a sound deadening spell inside the room to prevent noise from escaping.

You can use whatever materials you have on hand for this part. You can use magic items for this one.

　I'll use the materials and magic items I have on hand to repair the magic power reactor.
　In addition, I'll also modify the control unit to make it easier to use.

I'm going to have to say that this fortress was used in the era of the last dragon emperor.

　In the story Ryune told about the Dragon Emperor and the Dragon Princess, he told the story of taking all the dragon knights to battle with him.

　If that's the case, then the soldiers of this fortress must have gone to that battle or fought here to the end.
　It's ironic that this is being used as a hideout for demons.

But the structure of this device hasn't changed much since the last century.

　The fact that I didn't know about this fortress even if I recall my memories of my previous life, means that this remains were probably made after I died.

　But in spite of that, there hasn't been much progress in the equipment, does that mean that the era of the Dragon Emperor is not much different from the era of my death in my previous life?

All right, we're fixed!

　The repair was relatively easy to complete, so I immediately activated the magic power furnace.
　Then I felt a slight vibration in the fortress.
　When the work is done, I release the muffling magic and the sound of a loud siren jumps into my ears.
　This is the siren that warns of the enemy's invasion.
　Of course, the intruder that the siren signals is a demon.

　You can hear screams that seem to belong to demons from afar.
　I'm sure you'll be able to find a way to make the most of your time in the city.

'Yes, it looks like the defense system is still alive and well.

　In the prehistoric times, these fortresses were the most vulnerable to the intrusion of mages.
　That's why it was a top priority to incorporate the demon's unique wavelength into the defense equipment.

　That's why the power of the fortress was restored, the defense equipment that hadn't been broken yet started to work again, and began to exterminate the demons that had invaded the fortress.
　The demons must have been surprised by the sudden attack on the fortress that they thought was broken.

We always use the ruins of our era to our advantage. I think it would be a good experience to experience pain once in a while.

　And so, after a while, all responses disappeared from within the fortress.

'Looks like there were no humans in there.

　Yes, even though this fortress is a military facility and tough on intruders, they don't just kill people who are their own people. They would catch them and examine their backgrounds for the time being.
　But even so, the fact that every single one of the reactions in the base disappeared is proof that there were no humans inside this fortress.

　And as soon as the witches' reactions disappeared, the sirens also ended.

"This is the end of the demons inside the fortress!

　The kind of people who don't pay rent and live there without permission can't complain about being kicked out by force, can they?

　Incidentally, there's a reason why the defense device of the fortress doesn't respond to me who's not involved.
　That's because when I was repairing the magic power reactor just now, I used a nearby control terminal to sneak into the center of the defense equipment inside the fortress and registered me as a person related to this base.

　Well, it's a good thing the technical security of the control unit is so lax.
　How could I do that?

　That's because I was the first person in my previous life to create a magic building that incorporated and managed magic items into a building.

　The king in my previous life ordered me to build a semi-automatic fortress that incorporated magic items that could be used by a small number of people like a large fortress.

　Because of this, I knew the basics of magic construction, and I soon realized that it was an advanced version of the control system I used to build.

　Once the basics are understood, the rest is easy.
　The device, which was much more similar in structure to the one I had made in my previous life than I had expected, was easy to understand, and I soon transferred control of the fortress from the then administrator to me.

Now, let's resume our search inside the fortress. I hope there's a gate that leads to the demon's headquarters.

　You're not going to be able to do that.

　I decided to defeat all the demons, and I searched every inch of the fortress.
　I'm sure you'll find a lot of people who are interested in this kind of products.

The most important facilities are indeed elsewhere.

　It's a bit disappointing, but it's no surprise.
　This is the place the demons used as a temporary base.
　If they're going to set up a gate to get to the main base, it would be in the main fortress that has more defensive equipment.

''It can't be helped. Let's just be happy that we were able to eradicate the demons that were inside the fortress this time!

　By the way, the demon that I planted a marker in had also fallen inside the base.
　They didn't escape, and I defeated them normally.

''Well then, let's go home for a while.

　I activate my transference magic and return to the town where everyone is waiting for me.

I'll leave the rest to Majinhoi.

　You're not going to be able to do that.

　It was hell in there.

'Geez!'

　We had come to the rotting fortress of Dragonia to check on the safety of our lost compatriots.

'They've got Cordell!

　Then, as we went deeper into the city without finding anyone, a scream suddenly came from behind us.
　That was the gong that signaled the beginning of hell.

''Gwaaah!''

"RATHERM!

　The fortress's defence system, which was supposed to be stuck in place due to decay, had resumed its activities and was suddenly attacking us.

'd*mn it!　d*mn it!

　My compatriots attacked the defense device, but to my surprise, this device seems to have a magic item built into it that activates defensive magic, so the damage didn't go through properly.

''Run!　Anyway, we have to run outside!

　Oh, right, this was a trap.
　A horrible trap where the foolish intruder who entered the depths of the fortress would be hit from behind with all his might the moment he was caught off guard.

''Who in the world would set such a nasty trap!

　While we missed them as if we were on our way, a surprisingly large number of defensive devices intercepted us as we fled, and we never made it to the exit.

　We were wiped out before we could reach the exit, and those who came to investigate followed our path.

　Finally, after several failed investigations, our compatriots decided that this fortress had somehow revived its functions, so they gave up on further investigation and abandoned the fortress, but it was too late for us, who were already dead.