“Class” is something that accompanies the inhabitants of Niflheim from birth, the “Class” is influenced by the family into which the person was born, their personality, mana storage capacity and so on.

When referring to a specific “Class”, the word is written with a capital letter. Example: “Your Class is 'Missionary'”, but when referring to the generic job, the word is written in lower case. Example: “There are many 'archers' here.”

In the past, there were 7 demons known as Primordial Demons, their names were: Azazel, Belphegor, Leviathan, Mammon, Beelzebub, Asmodeus, and Samael.

The Primordial Demons united and founded the Inferno's Council. They gave rise to the “elite demons” and the “common demons”.

After the death of the 7 Primordial Demons, the elite demons founded clans under their names. As such, there are 7 clans in Inferno, although no members of the Samael clan have appeared so far.

The Inferno's Council demons' names are formed by their clan name, plus a preposition and their birth name, such as, “Azazel (clan name) van (preposition) Elsie (birth name).”

These are the clan names and their prepositions:

1. “Azazel van”;
2. “Belphegor dé”;
3. “Asmodeus di”;
4. “Mamon von”;
5. “Leviathan ford”;
6. “Beelzebub (preposition unknown)”;
7. “Samael (preposition unknown)”.

Currently, these are the positions of Inferno's Council:

1.  Demon King (held by a member of the Beelzebub clan);
2.  Inferno's President (held by a member of the Azazel clan);
3.  Inferno's Grand Duke (2 members of the Azazel clan);
4.  Inferno's Archduke (4 demons from different clans);
5. Inferno's Duke (12 demons from different clans);

In total there are 20 members of the Inferno's Council, however there are also Notables who have the right to attend their meetings, such as the Black Beast and the Devil of the Orient.

(Information regarding volumes 1-2.)

Saint is the title given to humans who have received the gift of conversing with gods. 

Saints get their power from the gods who guard them; they are the representation of their gods on earth.

The gods can give the “Holy Eye” to a Saint, which certifies that he is someone who possesses a bond with that god.

The “Saint” arbitration is unique, however a god can pass this power to another human, so the current Saint loses all his god-given powers, while the new Saint inherits those abilities.

Important Saints:

• Kurone Nakano (The “Saint of Heretics”, guarded by Cecily, Annie and Lucy). 
• Avios Bishop (guarded by Lucy)
• Malia (The “First Saint”, guarded by Astarte)

There are “Lower Saints”, which are titles of “Saint” given to a human by a Saint guarded by a goddess. An example of Lower Saints are Marquise Sophia Sophiette, the “Sword's Saint”, and Kawaii Kyuto, the “War's Saint”.

(information regarding volume 1-2)

Name: Kurone Nakano.

Other names: Saint of Heretics (vol. 01).

Age: 20 (vol. 01).

Gender: Male.

Nationality: Japan.

Race: Hybrid/Chimera.

Elemental Type: Fire, Shadow.

Main Spells/Skills: Holy Eye, Orc Summoning, Internal Storage, Mana Sharing.

About:

Kurone Nakano was an ordinary young man from Tokyo. Due to events related to his childhood, he grew up with serious mental problems, which led him to be expelled from several schools.

When he entered medical school, he began psychological treatment to deal with his mental problems, but this was interrupted when he was reincarnated in the world of Niflheim. 

Kurone was born with the sole purpose of killing Goddess Annie, however, as an irregular being, he went against his destiny and decided that he would live to save Rory

(The above information refers to volume 01 and will be updated as the story progresses)