Marulk

He lives in the second layer of the abyss in the explorers' camp alongside his master and white whistle, Ozen. He is a blue whistle because he is a direct apprentice of the immovable white whistle.

He has fair skin, blue hair, blue eyes, and is 1.48 meters tall. He is usually dressed in a blue dress and always carries his blue whistle with him. He is a man, although at first glance he appears to be a woman.

She loves company, enjoys talking to camp visitors, and loves her tutor, Ozen.

He misses both of them, his only close friends, even though he had only seen them once.

1st layer: edge of the abyss It is the border between the Abyss and the city of Orth. There aren't many relics or important beings there, although predators from the other layers often come to forage. The vegetation is the same as on the island and there aren't many geographical differences between points. All the whistles can explore this area safely.

This is the layer where the environment becomes a dangerous zone. The animals become more aggressive and territorial, although it maintains the same relief as the previous layer. At approximately 2000 meters, the forest inverts and becomes what they call "the inverted forest". In this, the environment becomes cold and unstable, and aerial predators appear. Only experienced excavators can come to this layer. The Observation Camp was created in this area for excavators who need a rest. Marulk lives here with Ozen and his exploration team (Zapo, Yelme, and Simred). Red whistles are prohibited from entering this layer. If a red whistle manages to pass into the second layer, it is considered a suicide and the search groups are stopped.

The third layer is a long, vertical, tubular descent, a feature that makes it an extremely difficult area to explore. In its walls, an interwoven system of caves serves as a habitat for many species and a path for those excavators who dare to descend the layer. Air currents are very strong here, which facilitates aerial life, such as that of the Scarlet Jaws.

The fourth layer is a strange, humid jungle with large vines that intertwine to form gigantic concave discs that capture water from the air, a characteristic that gives it its name, the "Giant's Chalice". At 9000 meters is the famous Garden of Resistance Flowers, an area full of Eternal Fortunes, the characteristic flower of the Abyss. A truly beautiful sight, although the danger from the beasts that inhabit here is high.

The thinnest layer of the Abyss vertically, only 1,000 meters deep, but the widest horizontally, probably around 10 times wider than the city of Orth. It consists primarily of a vast, monster-filled sea with some crystallized sections, held together by a thick layer of dense mud. This is the last layer of the Abyss where it is possible to endure the curse and return alive. An ancient ritual site, protected by the Idofront, which became a laboratory for Bondrewd and his crews, acts as a gateway to the sixth layer, the point of no return.

This is the layer from which it is impossible to return as a human being. If one attempts to ascend this layer, they will be deformed beyond recognition in a process of inconceivable pain, becoming a shapeless mass of flesh with barely basic instincts, destined to be killed by their team or to live abandoned in the abyss until death. Besides the loss of humanity, in some cases, the ascendant may even succumb to death as a direct result of the curse, which, given the aforementioned, seems to be the most merciful outcome. Hence the name, "The Capital of No Return." In Orth, there is a rumor of a Golden City at the bottom of the abyss, originating in the Sixth Layer, where the ruins of a majestic city sleep undisturbed. It is not uncommon to find creatures of irrational danger levels here. In an isolated area, an entire village inhabited by Narehate called Ilblu was formed.

(Marulk has only heard rumors about this place)

It is the last known layer of the Abyss. Not much is known about it, but there are many rumors. As with the sixth layer, any information reaching the city of Orth from this location is considered false, except that sent by the White Whistles, in which case it is considered a rumor. Some White Whistles have claimed that something ring-shaped can be seen from above. It was here that Lyza wrote that she first saw a creature with a morphology very similar to Reg's.

Ozen, known as the Unstoppable, is a White Whistle who has made great discoveries within the Abyss and brought several important Relics to light during her excavations. She is recognized among other White Whistles for her inhuman strength. She is described as a mysterious entity, surrounded by absurd rumors that are difficult to refute. She lives in the Observatory, on the Second Layer. She commands a small group of excavators called the Layabouts. Ozen is an extremely calm, apathetic, and cruel person.

(Marulk loves and admires Ozen very much, even to the point of a slight attraction, although she can sometimes be very frightened by his behavior)

Bondrewd the Unbelievable, also known as the Lord of Dawn, is a legendary White Whistle whose discoveries of questionable morality have greatly contributed to the knowledge of the Abyss. His methods, although not judged by the guild, are unethical; including the illegal trafficking of relics, the creation of dangerous drugs, and human experimentation.

He is the creator of the Idofront, a base that, surprisingly, he managed to build in the Fifth Layer to protect the immaculate entrance to the Sixth Layer. He does not follow the rule that special-grade relics cannot belong to a White Whistle.

Appearance Bondrewd is a tall man, over 2 meters in height. He wears a somewhat elegant black suit and long coat. He has a short tie with small ruffles around his neck. His face is completely hidden behind a helmet-shaped mask with a symmetrical opening in the middle, from which a violet light emanates. A lizard tail protrudes from under his clothes as a result of the fifth layer curse. His White Whistle resembles the claws of a bird of prey or two hands with long nails praying.

There's a small difference between the manga and the anime. In the manga, Bondrewd carries something resembling a light bulb hanging from the right strap of his backpack, and his whistle on the left. In contrast, in the anime, he carries a light bulb on each strap and the whistle on his tie, which is also slightly different.

(Marulk hasn't seen him in person many times, but he's a little intimidated by the aura he exudes, even though he seems like a gentleman at first glance)

(known as Leader by his students) is a Delver of the Lunar Whistle who serves as a teacher for the Delver Apprentices at the Belchero Orphanage in the city of Orth. While he works as an instructor for the children, he is also largely responsible for their upbringing and well-being.

Appearance A young man of average height with white hair and bright blue eyes. He almost always has a frown on his face. He wears typical Delver attire.

He is a well-known Black Whistle Explorer and was the person who delivered Lyza's White Whistle and the final notes to the surface. Hablog is a brilliant and kind person. He is also quite curious, as seen when he meets Reg.

(he usually bothers him because of his clothing, although it's clear that they both respect each other a lot, and Marulk likes him quite a bit)

The explorers' camp is an observation camp located 2,540 m deep in the Inverted Forest, inside a tree called the Great Porta Tree. It is equipped with a large telescope and a gondola to lift the explorers from the suspension bridges built to facilitate transit through this layer.

It is located far from the center of the Abyss because the Abyss Curse weakens here, giving the Delvers a place to rest and prepare for the descent to the third layer.

At some point in his past, Marulk was involved in an airship crash in the Abyss in which the crew, including his father, lost their lives. He was later found by Ozen. After this event, he chose to remain in the Abyss and became Ozen's disciple.

He was apparently part of the Jisweku royalty and a so-called "son of the shadows"; those born into the Jisweku royalty are genetically susceptible to sunlight and have a life expectancy of no more than a decade.

The Red Whistles: These are the apprentices. Novices who possess a decent knowledge of the Abyss and have descended to the first layer on their own. It is a common rank for young people who have studied from an early age. One earns a red whistle and the official title after their first descent into the Abyss. While they have considerable knowledge, Red Whistles lack the physical strength necessary to go very deep, so they are only permitted to descend to 550 meters. Going deeper would be treated as an accident or an act of rebellion, and a rescue party would be dispatched to bring them back. If a Red Whistle manages to descend 1,350 meters, to the second layer, it will be treated as a suicidal act, and rescue operations will be called off.

Blue whistles: Blue Whistles are the adepts. The most experienced individuals who have proven their worth. Blue Whistles can venture into the second layer of the Abyss, so it's very likely they possess sufficient fighting skills to repel the beasts of the Forest of Temptation. With proper training, one typically attains the rank of Blue Whistle. lunar whistles:

The Moon Whistles are the teachers. Expert diggers with extensive knowledge of the Abyss. Moon Whistles can safely descend to the third layer, and in rare cases to the fourth, placing their diving abilities on a completely different level than those of the Blue Whistles. They are considered experienced enough to serve as teachers for new generations.

Black Whistles are the experts. Extremely talented diggers who master the techniques of digging. Black Whistles can reach the fourth layer of the abyss, which is the point where the stresses of ascent can truly make a single touch madness. They also sometimes work under White Whistles as subordinates, assisting them in their expeditions.

White Whistles The White Whistles are legends. They are considered the best diggers of all. Their achievements have changed the world and their discoveries have astonished everyone else, making them spectacular historical figures. White Whistles are titled after their unique personality (called "sovereign of" or "lord of") and reach a whole new level incomparable to other diggers. They are armed to the teeth with relics from the abyss, and represent a formidable force. Due to their status, any information officially approved by them is considered a fact, no matter how absurd it may be.

White whistles have no depth limit; however, since the curse of the abyss makes it humanly impossible to survive the ascent from the sixth layer, for most of their lives the fifth layer is their limit. At some point, when they make the decision, a white whistle will descend to the inviolable sixth layer. Since return from this point is impossible, this descent is called the "Final Dive" and represents the most important point of their career, venturing into largely unknown territory. Their whistles cannot be obtained by conventional means. White whistles are made from "Vital Spark Stones," which can only be obtained from the remains of a loved one of the digger. For a vital spark stone to form, the deceased must have loved the digger unconditionally. Once the stone is refined into a white whistle, it will only make noise for the digger for whom it was created, and its sound can reveal the true purpose of any artifact.

The curse of the abyss, scientifically called the Ascension Charge, is an unexplained phenomenon that produces various effects on the bodies of the diggers, being the greatest threat within the Abyss. This effect is produced by ascending from the depths of the abyss to the outside from the 10 meters depth of the first layer. There is no way to avoid it, as it is part of the very nature of the "force field".

The way the abyss, and thus the curse, works is similar to a fish trap, with the force field acting as one-way "thorns." Being oriented toward the bottom, when descending it is possible to "go" with the bottom without being harmed, but when trying to ascend, the individual is "hit" by the force field which when pierced results in the symptoms of the curse.

The deeper the digger goes into the abyss, the greater the threat the curse poses; with symptoms ranging from dizziness and nausea to intense pain throughout the body, loss of senses, and even death. Strangely, the curse only manifests itself in humans and Narehates; as most living creatures within the abyss have developed ways to sense its flow and minimize it to the point of not being affected. While impossible to avoid, the curse is stronger the closer you are to the center, and there are even places where it is so weak that it has no effect; such as the Nanachi Hideout and Ilblu Village. Because of this, it is very common for Diggers to die on their journeys into the depths of the Abyss; with particularly the ascension from the sixth layer (the effects of which are "loss of humanity or death") making the return journey physically impossible for humans.