Long has the language of evil beings existed, often given in visions and found written in the blood of dark rituals this is the lower language used by creatures commonly referred to as demons. Speakers of this language are generally demons or have some relation to them such as the Nephilim race but it is not considered to be a widely accepted language to use because of its origin. The script for Infernal is menacing and looks as if it were written by a creature in agony, those that observe it will often feel uneasy without an explanation as to why even if they do not know what language that it belongs to. This language is often used in dark rituals, histories of evil creatures, and curses.
The earliest appearance of this language is unknown which leads many scholars to believe that it is older than the appearance of any race in the world of Isekai. Throughout history, it has been present at intervals and appears fully with the emergence of the Nephilim race as a fully realized language and connects them to a heritage that many despise to this day. The Infernal language is constantly associated with the cosmic beings that stand in opposition to the gods, more specifically the ones that plague the races of Isekai directly and often seek to be summoned into the world so that they might create an anchor and remain in it. Because of this, the Infernal language is considered taboo to use whether spoken or written in most circles and cultures of the world except for the land of Nephilim, the Fire Islands. There the language is used as a day-to-day speaking and writing method while the inhabitants have no fear of using it, rather it seems to be a cultural statement that they have claimed the language as their own.
The advantages of speaking this language are directly related to being accepted in the Nephilim culture or by invoking the power of beings that stand in opposition to the gods. If you speak and read Infernal it is assumed that you are using it to understand the movements of cults, evil creatures, and demons that have come to this world which will mark you as either a crusader of light or as a servant of the darkness. Intellectually, it is seldom studied except by spellcasters and professions that have an interest in thwarting the summoning rituals of demons. Regionally, the entirety of the Fire Islands uses this language as their main spoken language, and being able to use it will gain you much easier acceptance into their culture as it communicates to them that you do not mark Nephilim as products of their ancestry.
Writing System
Interesting history behind the language. I like that it's only studied by a few.