Monster

Monsters are a variety of non-sentient beings from Tortus. They have a unique trait of being able to manipulate Mana, without the need of any magic Circle or Incantation, and each one of them has a unique racial skill, ranging from ranged attacks to faster movement.

Monsters are created naturally when an animal has enough mana absorbed into their body that transforms them. As a result of this process, monsters have cores of crystallized Mana in their bodies that can be of great value. They gain powers by eating the flesh of humans and other monsters.

Monsters can be artificially created by someone in possession of Metamorphosis Magic.

Regardless whether consumed raw or cooked, monster meat is extremely poisonous and lethal to any human that consumes it, as doing so would trigger rapid deconstruction-reconstruction of the body on a cellular level, the resultant trauma is beyond human body to handle on its own, unless be able to rapidly regenerate and heal itself. The only way known to be able to survive after consume monster meat is through consuming ambrosia, a drink formed of Mana condensate secreted from a legendary crystal known as the Divinity Stone when the latter eat the monster meat and drink the liquefied Mana and turn into a human/monster hybrid but not considered as humans anymore as a cost for their mutations.

Monsters are normally non-sentient beings and the only way to gain true sentience, is by drinking Ambrosia.

Sea-based monsters are more attuned to sensing sources of Mana than other monsters due to using it as a way to navigate while their other senses are dulled underwater.

Great Orcus Labyrinth
Monsters in the Labyrinth are part of its eco-system, and have a mechanic built inside them which makes the re-spawn again after a certain time after they had been defeated.

Upper Levels
Found on the 1st floor, it's a giant muscular rats that stand on two feet. Only the area around their corded chests was bereft of fur. It's quick on its feet, but not that strong.
 * Ratman (ラットマン):

Found on the 20th floor, it's a gorilla-like monster that can camouflage itself.
 * Rockmount (ロックマウント):

Found on the 65th floor, it's a powerful monster with a huge body of 10 meters length. Its shaped similar to a triceratops, with a head like that of a bull with two huge horns sprouting on its head, and has glowing red eyes.
 * Behemoth (ベヒモス):

Found on the 78th floor, it's a mud doll in the shape of a person that can morph its appearance.
 * Clay Golem (クレイゴーレム):

Lower Levels (Bottom of the Abyss)
Found on the 100th and final floor of the Labyrinth, the "Hydra" is the last Final Boss and Guardian, that one has to defeat in order to complete the trial of the Labyrinth. Being the Final Boss of the Labyrinth, it is also the most powerful and strongest monster in the entire Labyrinth, having extremely high stats and unique skills to utilize. Physically, it looks like a huge serpentine creature, with a hard shell body and six-heads. Each of the heads of the Hydra are differently colored (in the LN and Manga, each one had a different-colored pattern engraved into its head instead) and a pair of dark red eyes. Each head has its own unique ability along with physical attacks, which compliments the other heads, thus being akin to a perfect balanced party.
 * Hydra (ヒュドラ):
 * "Red" Head - Fire
 * "Green" Head - Wind
 * "Blue" Head - Ice
 * "White" Head - Healing
 * "Yellow" Head - Defense, limited ability to morph surrounding terrain
 * "Black" Head - De-buffer/Illusion, inflicts Fear Status

Reisen Gorge
A giant winged monster that is similar in appearance to a.
 * Hyveria (ハイベリア):

Great Gruen Dessert
A winged monster that sleeps under the sand and uses that desert's sandy winds to travel and prey upon its target. It has special magic that lets it absorb the water in its prey’s body by biting them.
 * Sand Bat (サンドバット):

A large earthworm-like monster that only resides in the Gruen Dessert. They are 20 meters long on average, and some of the really large ones grow up to 100 meters. They normally live underground and only surface to swallow their prey with their triple-layered circular maws. They do not, however, possess good perception abilities, and would only attack if someone accidentally walks over their lairs.
 * Sandworm (サンドワーム):

A small fish-like monster that swims in the sand and possession powerful jaws.
 * Saw Fish (をた):

A bat-like monster made out of magma. They are capable of expelling magma from their wings
 * Magma Bat:

A lizard-like monster made of magma. It has a whip-like tong that it attacks with.
 * Magma Chameleon:

An eel-like monster capable of melting solid walls as it travels.
 * Magma Eel:

A bull-like monster made out of magma.
 * Magma Ox:

A porcupine made of magma. It can shoot flaming spines from its back.
 * Magma Porcupine:

A snake-like monster made out of magma.
 * Magma Serpent:

Frost Caverns of Schnee
An eagle-like monster made out of ice. A giant turtle-like monster made of ice and has six legs. A wolf-like monster made of ice.
 * Frost Eagle (フロストイーグル):
 * Frost Turtle (フロストタートル):
 * Frost Werewolf (フロストワーウルフ):

Monsters Created by Dienleed Galdea Vesperitio Avatarl
A giant monster found as the guardian inside the room on the 50th floor of the Great Orcus Labyrinth. It's shell is made of shtar ore that hardens whenever it is exposed to Mana, and can also shoot out acid-filled needles. Since this monster isn't originally part of the Labyrinth's eco-system, it won't re-spawn after being defeated. It was created through a combination of both metamorphosis and creation magic.
 * Scorpion (サソリモドキ):

Monsters Created by Freid Bagwa
A monster with two heads, four limbs, and wings. It possesses the special magic "Camouflage", which enables it to blend into its surroundings, as well as anyone that touches it.
 * Chimera (キメラ):

A butterfly-like monster that can fire heat rays. A large beetle-like monster that was able to propel itself with special organs on each side of its wings that allowed it to jettison Mana that is increased its speed, as well as control its direction. A flying leaf-insect-like monster. A giant bee-like monster. It has six pairs of thin wings.
 * Cyuveria (サイヴェリア):
 * Dryger (ドライヤー):
 * Ozmuse (オズムセ):
 * Squier (スクワイア):

Others
A type of slime monster that possess the special magic "Mimicry", which allows it to morph its appearance to the extent of changing its colors or vaguely imitate the shape of something else. A bird-like monster. They are not strong, but they attack in flocks by raining down their razor sharp black feathers at their prey, while maintaining a safe distance from the ground. A monster that lives in the northern mountains. They are a cross between orcs and ogres. They are a powerful race known for their high defensive capabilities, and possesses the special magic "Steel Skin", which is an inferior version of "Diamond Skin". They aren’t very intelligent, but they always roam in packs.
 * Bachulum (バチュラム):
 * Bahal (バハル):
 * Bulltaur (ブルタール):

A large bird-like monster that can fire needles that petrify anything that comes into contact with it.
 * Cotriss (コートリス):

A wolf-like monster. They are nimble and hunt in packs. A giant gelatinous sea-based monster. It is able to constantly regenerate whenever it is injured, as well as excrete corrosive jelly that is even capable of dispersing magic. They are so dangerous that they are seen more as natural disasters than monsters. They were originally created by an ancient civilization in Tortus.
 * Delose (デロス):
 * Devourer/Hell Eater:

A fish monster with a human-shaped head. It is able to use the special magic "Telepathy" as a way of communicating. It is the only known monster that is sentient and not hostile towards humans.
 * Fishman (リーマン):

A small monster with dark-green skin.
 * Goblin (ゴブリン):

A monstrously large sea-serpent that was sealed away by the gods of Tortus with the island Andika.
 * Divine Beast Leviathan (リヴァイアサン):

A tree-like monster. It is able to convert sunlight into energy to enhance its Mana, physical strength or other stats. It also possess special magic "Regrowth", which allows it to sprout as many trees as it wishes, and control them freely.
 * Treant (トレント):

Human/Monster Hybrids
Human/Monster hybrids are a rare and unique species of humans who have gained a monstrous appearance and inhuman strength through mutations from consuming monsters' meat and drinking liquefied Mana. The changes the experience from consuming monster meat includes their original bodies becoming muscular and taller with purple spiked bloods cells, red tattooed-like veins even both their hair turned from original to white and eyes turned to crimson red, as well as their Mana turned from normal to crimson. Their strength, speed, and senses are stronger then beastmen and ordinary monsters, and their Mana is even more powerful than normal Mana blessed humans and demons as their strength and abilities are completely inhuman and monstrous.

It is worth noting that such hybrid is an accidental result of surviving the agonizing mutation process, which is otherwise unsurvivable as the subject undergo rapid cellular reconstruction soon after consumption of monster flesh. The resultant trauma would have been lethal without immediate intake of ambrosia, which is mana in condensate form typically found secreted from Divinity Stone, to allow subject recover fast enough to survive. The exact mutation process is never well understood for the critical item - ambrosia - is legendary rare that even scholars would most likely only read of it in ancient text, lest to even realise its role in surviving the mutation process. The mutation is more than cellular level, it's right down to DNA level. Suffice to say, the subject is no longer human, even aura is more akin to monsters than that of humans.

Now with the body systems adapted to process monster meat, a hybrid can further increase one's stats from consuming monsters stronger than oneself, and gain new special magic/skill/passive buff from the monsters that one absorbs. Like monsters that use their respective magic/skill instinctively, a hybrid can also instinctively use absorbed skill/magic without chants.

To date, the the only successful survivor of such mutation process is Nagumo Hajime.