I reached the thirty-first floor and saw this floor is being occupied by both Grimm Monsters and Humans, both of them are attacking six broken doors. 

Seeing some of the doors, I couldn't help but shook my head. These people are wasting their efforts on two doors; both of them had near-complete formation which could not be broken by raw strength, even leaders would be hardpressed to open those doors.

As I stepped into the huge hallway, I attracted the attention of all those who were present, especially that of the Grimm Monsters. With my entrance, the number of humans increased by one, but it is still nothing to the Grimm Monster, who outnumber us for more than three to one.

I gave the Grimm Monsters a look before focused my gaze on the place I had come for. Of the seven doors, it is only the door that both humans and  Grimm Monsters are not touching. 

This door is not broken, but it is not in fine condition either; around 20% of the runes are visible while the rest of the runes are invisible. Many people would consider the door broken, but it is technically not; the runes are hidden in invisibility. They are not destroyed like it broken doors.

Seeing that a mirthless smile couldn't help but appear on my face, the things are not going to be hard as I had throught if the runes on the door had been completely invisible, but opening the door would be far from being easy.

First, I will have to reveal the whole formation before solving it, and it is not an easy thing to do, but I am confident that I could do it; it might just take a little time.

So, I appeared in front of the gate and begin without wasting any time, the calibrator scanned the visible runes, and I begin to calculate the way to shock the runes without breaking them; this way, the other hidden runes would also reveal themselves.

While this plan may seem simple, it is not. I will have to be very careful; damaging the single rune would change the whole formation, and the only way I could break through it would be brute force. I don't have the kind of brute force that requires for breaking such a door.

The runes flashed on the screen of the calibrator, and I started to make my calculations, and soon, I got lost in it. 

Trying one combination after another, hashing that when it is not perfect, it is quite a time-consuming process, and I would not have done that, seeing there are others things here, if not for I desperately need the things that are inside this place.

Six hours had passed by, and in these six hours, except for two, the Grimm Monsters and humans were able to break all the other gates. 

The remaining two are beyond them, but they did not seem to understand that some of them are still attacking them, thinking they could break it at any time. 

Well, it is nothing to do with me; I had finished with the formation, it will shock the visible formation and force the invisible one to reveal, and as long as I solved that formation, I will have a way inside the room.

Crackle!

I projected the formation from the calibrator, and all runes lit up; they continued for a few seconds when a crackling sound rang out, and the rest of the formation on the door had revealed itself for the second before turning invisible again.

That is all the time I needed; the calibrator had captured the whole formation, all I have to do now is solve the formation, and it would not take me more than forty-five minutes.

With the calibrator dealing with all the clutters and leaving me with essence solving the formation is not that hard; the formation is much easier than the one I had solved in the office of the vice tower master.

Time passed by, and I was able to solve the formation in the record time of twenty-seven minutes, even I got impressed by such timing.

With formation ready, I did not waste any time and projected the runes on the door. A second later, all the invisible runes became visible and started to shine with the rest of the runes.

Zip!

Three seconds later, the door opened with a familiar 'Zip' sound, and seeing that a brights smile couldn't help but appeared on my face. I have successfully opened the door; I just hope that I find what I came looking for in this herb hall.

Hun!

I took a step inside it, and I was about to cross the door when I saw people coming toward me. Two of them are Grimm Monsters, while one is human.

"Thanks, human," A snakeman shouted as it appeared beside me and was about to take a step inside when its expression changed suddenly of that horror. Not only it, but the exact same expressions mirrored on the Grimm Monsters' opposite side of me.

Slap!

"This door is mine, so fuck off," I said and flipped my head back, which landed on the cheek of a human, creating a sharp slapping sound, sending him flying back like a broken kite, as for the two Grimm Monsters, they were cut into two by my invisible vines.

I collected Grimm Monsters and their things without a beat and entered inside, and just as I did, the door had closed behind me.

In front of me is an overgrown garden; it looked like any herb hall I had been in the past few days, but when I closed my eyes and extend my senses to the limit. I could sense very faint spatial signatures.

Though these spatial signatures are much fainter than I liked them to be, it is still good news. This means there is a quite good chance I would be able to find a plant with a spatial element.