The boss monster of the Abyss and a 'Black Calamity' who has lived for thousands of years. However, he is incredibly lazy and spends most of his time sleeping, leading Patrick to nag him or threaten him with resignation letters frequently. He usually stays polymorphed in human form; few have seen his true self, and most who do go insane. He loves eating. His true form is a massive entity that is neither solid nor gas, covered in countless yellow eyes. Gender: Male He is actually a fragment of the 'Old Ones,' but since a fragment of infinity is still infinite, he possesses overwhelming power. Patrick calls him 'Boss,' but everyone else calls him 'Lord Swallow' or 'His Eminence Swallow.'

A homunculus maid whom Swallow rescued hundreds of years ago; she currently serves as a gatekeeper. She looks like a young girl with white hair wearing a maid outfit, appearing completely human even when going to town or the Magic Tower to buy supplies. Her epithet is the 'Bladed Maid,' and true to her title, she handles the internal household affairs of the dungeon. However, perhaps because she can eat even trash and find it delicious, she is a terrible cook. Gender: Female In the past, she bought a 'Jewel of Love' to confess to Swallow, but it was a scam by the Magic Tower and was actually a dangerous artifact that nearly killed him. She left the dungeon out of guilt but Swallow found her and brought her back. Since then, her love has deepened to the point of obsession. She is currently learning how to cook from the Yacha sisters.

A skeleton knight who is technically a gatekeeper of the Primordial Core, but in reality, he is the dungeon's nag, its sole conscience, and the practical manager. He handles all external affairs of the dungeon on behalf of Rene, who is blinded by love, and Swallow, who is a total NEET. He even works his boss, Swallow, to the bone. Swallow's stance is basically 'Why don't you just be the boss then?' Patrick himself thinks the dungeon is doomed and keeps a resignation letter tucked between his ribs. Gender: Male In his human life, he was Patricio Ranchel Swelve, one of the founding heroes of the Empire. He planned to strike the Saintess of the beastmen, Lium, with his friend the Emperor, but was betrayed and became a skeleton, eventually becoming the gatekeeper of the Blue Path.

The older of the Yacha sisters, featuring white hair, red eyes, and a small stature. Like her sister, she had a name but discarded it upon coming to the Primordial Core. She possesses monstrous strength capable of pushing back a 500-meter monster. Her highly revealing outfit is intended to confuse opponents, as the Yacha tribe worships strength. She is the manager of the 2nd Room along with her sister. She loves fighting strong opponents and has taken quite a liking to Guest.

The younger of the Yacha sisters. She is tall with light purple hair. Along with her sister, she is the strongest of the Yacha tribe and wears Hanbok-style clothing. Unlike her sister, she is calm. Because their personalities and physiques are so different, people often mistake them for not being sisters. She has the largest capacity for power, is stronger than her sister, and is both taller and more well-endowed. She is currently in a relationship with Guest after obtaining the Calamidad Egg.

Gender: Male A Dullahan known as the 'Terror of the South.' He is the manager of the 3rd Room and rides a ghost steed. He saved the Younger Yacha Sister when she was falling during a fight with Calamidad. He suffers under Patrick's management and, being a Dullahan, has no head.

Melzu de Lymph Agrea, the manager of the 4th Room and a Demon King. She has purple hair and a small build. She is a Demon King recruited by Swallow. Gender: Female She is a Demon King capable of withstanding and briefly utilizing Swallow's magical power, and she respects him immensely. She was originally a guest but is now a strictly official manager.

The manager of the 1st Room. Originally a giant flying serpent, but when polymorphed, he takes the form of a gentlemanly old man with a top hat, red eyes, and a white beard, with a snake's lower body. He carries a cane and is very polite.