Devil's Labyrinth  is a dungeon that was created within Seryuu City by an Eyeball Demon. During its formation, the demon had also trapped various people inside the dungeon that was within the vicinity during its creation, including Satou. The mana from Seryuu City's Source is currently being siphoned by the Devil's Labyrinth.
Entrance: Middle of Seryuu City
Dungeon Master: Arm Demon/Senior Demon that attacked the lord's castle in Seryuu City.
The paths inside branched out like the roots of a tree to form various rooms, then diverged back into more pathways. There were areas that crossed through multiple levels and shortcuts connecting other rooms, too.
Contains a gate with 『Thou hast to answer my question if thy wish to continue』written on it. The riddle to open it is 『Shonimu is righting the tree, Dareson is eating the fruit, Yurato is planting the seed. Correct our right position.』The key items to solving the riddle are each contained in different rooms.
- Room with statue on top of a pedestal in center of a room with a depressed floor except at center and Wandering Roots, tree root like creatures, surrounding the statue. This is the room closest to the gate. The statue is the key item to solving the『tree』part of the riddle.
- Square room with a Lv40 Stone Golem, 3 meter great-majin look-a-like monster, in the center of the room. The center is of slightly lower floor level. The Stone Golem has [Physical Damage Halved] and [Spirit Damage Invalid] unique skills. After defeating the Stone Golem, a blue gem can be obtained to solve『fruit』part of the riddle.
- Room with treasure chest in center and surrounded by traps. There is only one safe path leading to the treasure chest. The treasure chest is actually a Mimic, which Satou considers a regular dungeon monster. When defeated, it evaporates into purple smoke and leaves behind a black stone, which is the key item to solving『seed』part of the riddle.
It is unknown what the correct order to placing each key item is since Satou used the [Deriddle] skill to solve it.
The dungeon master is in a room containing an alter with candles around it. When one enters the room, the candles light up with blue flame and a magic circle with purple light, from which the demon appears from, emerges on the alter.
Satou first entered the labyrinth when it first appeared and entered it again at night, when nobody was around, to defeat the dungeon master.
- Insect monsters with levels around 10-20.
- Gigant Cricket: Ramming and Biting.
- Caterpillar: Spitting venom.
- Snake and Frog monsters.
- Rat monsters level 10 and weak.
- Giant Frog level 10: with tongue as a special skill, they have internal organs with poison.
- Undead Beast: undead kin, 5 meter length, 2 meter height. Jet black panther-like beast with a red horn on its forehead: It bite can paralyze, attack include the claws. Very agile. Weakness: Holy element. Level 40.
- Undead Beast: enormous body, jumping power is heavy and powerful, roar, biting attack. Like the other Undead Beast but with 2 horns.
- Spider monster: spider silk make cocoons, overhead sweep of the spider's leg.
- Spherical Demon with wings level 35 (also call it Winged Eyeball).
- Skeleton Knight, Skeleton Deathschyte, Skeleton Warrior, all of them on level 30.
- Skeleton Soldiers level 10-15 (also call it Zako).
- Tree root-like creatures call it Wandering Roots.
- 3 meter great-majin look-a-like monster, its a Stone Golem. Level 40. It has [Physical Damage Halved],[Spirit Damage Invalid] unique skills.
- Mimic, it looks like a treasure chest, attack by opening its mouth.
- Black Demon: black aura is rising from its body, this is the support magic [Physical Damage 90% Cut], a purple lights are emitting from its nails, horn and tail, this increase the [Physical Attack Power 300% Up], the demon stab the poisonous claw, use the rotating tail to strike.