Before challenging the 『Floor Master』, I investigated the monsters and the terrain here with 【Passive Detection】.

  It's normally not possible to defeat a 『Floor Master』 alone.

  If it was the past me, I could just shoot some random magic to evaporate the monster along with the dungeon from where I stand, but the current me has lower magic capability than even an average magician in my past life. I can't use that kind of brute force method.

  Even with all of my knowledge and experience, I still need to plan a way to defeat it.

  I'm going to pick a place to fight based on the flow of mana and terrain.

  The battlefield has to satisfy two conditions.

  First of all, there should be as few passages as possible that connect to that place.

  One of the basic in challenging a 『Floor Master』 is to exterminate the whole monsters that dwell on that particular floor to prevent them from barging in during the fight.

  In addition, you want to break down the floor's walls to create a huge space for many people to fight at once.

  However, I can't use that method this time.

  The need to exterminate other monsters on a floor is applicable when it's a raid subjugation.

  For me, doing that alone would waste too much mana and time. It's impossible.

  Therefore, I'm going to narrow down a place with few passages that connect to it to decrease the possibility of monsters intruding in.

  Even if other monsters barge in, I can just cope with it if I just anticipate them with 【Passive Detection】.

  Secondly, it has to be spacious.

  The Fourth Crest is normally better in a narrow space, but when you're fighting a 『Floor Master』, not having enough space to dodge its attack is out of question.

  After all, the current me would die if even one of the 『Floor Master』's attacks hit me——

  Fortunately, I immediately found a place that meets those conditions.

  It's a huge room 80 meters away from the place the 『Floor Master』 is lurking.

  I went into that room while cutting down all monsters I met along the way to reduce the chance of them intruding in even a bit.

  The ground is flat, the ceiling is high, there are only two passages that connect to it. It's perfect.

  And since I've gotten closer to the 『Floor Master』, I've completely grasped the kind of monster it is.

  It's a huge venomous snake monster called 『Arch Serpent』 in my past life.

  It's hard to treat it as a source of material, but at least I've gotten ahold of its identity——

  And so.

  "Now come!"

  I invoked 【Compulsion Detection】 at the 『Floor Master』 while shouting out loud.

  In order to make the Arch Serpent separated by several layers of walls, dozens of meter away notice me.

  Then I heard roaring sounds from the direction of the Arch Serpent.

  Using 【Passive Detection】, I see that it's coming straight at me through the shortest route while ignoring walls.

  And about two seconds later.

  The wall in front of me suddenly dissolve as the Arch Serpent showed itself along with purple liquid.

  The purple liquid is an Arch Serpent's most peculiar characteristic, it's a strong acidic venom.

  The venom isn't stopping at only dissolving the wall as it begins to gradually dissolve the floor which should have been far resistant to acid.

  "…Oy oy. There's a passage over there, use that instead of breaking things please…"

  Now a terrain I've especially prepared for the battle is ruined.

  I can't rely on the ground at least.

  My shoes will melt if I step on the ground where the venom fell, and even if I have acid-proof shoes on me, those hollowed grounds are useless as footings. Even if the surface looks fine, it's not unusual for the inside to be hollowed out.

  I can fight by putting up barrier magic under my feet for an instant as my footings.

  And since the venom is volatile, it will pollute the air if it takes too long.

  The air will only be safe for battle for at most 10 minutes.

  Now then. It's the first tough-looking battle since I've obtained this Disqualified Crest.

  Short it may be, let me enjoy this fight to the fullest.