This world only has a few selection of Demon Creatures that have been brought into this world by The Demon Grandfather, Khalfvyskov. He has bought a total of 10 types of creatures into this world each with their own unique identifier. These demons were created to life in the year of 55 AD, and they age at the same rate, with their age measured in days.
Khnavkiers. A direct demon-descendant from Khalfvyskov himself. They look like a combination of minotaurs, onis, and chimeras
Lesser Witches / Demon Witches. Among the creatures, comes Lesser Witches. They all come in different appearances, but that's their main form. They can fully evolve into a demon witch through countless bloodshed.
Devil/Demon Angels - Fallen Angels Demon Orges Gorgons Imps Djinns Demon Mages Tainted Serpents Devil Snakes
Each Demon Creature in every different subrace will age slowly after 23 years. At the age of 23 is when demons get their abilities and powers after undergoing a process called Demonization. Demonization happens when every cell in a demon body becomes unstable due to the changing effects of black blood cells. The unstable cells turn into Demon Core Cells, which each develop their own unique abilities and powers. After this process is done, the aging factor is slowed down during that 23rd year. In a dormant section of a demon brain, those powers and abilities become a part of their survivability. They are powerful to their own accord. All Demons have two hearts.
It takes 975 years for a demon to reach 155 years old (biological age). The oldest age they can live up to is 9,000 years old. The ages of baby-23 needs to be dismissed, because those years are when they age much like how humans age.
975 - 23 = 952
952/23 = 41
41 years of life is equivalent to 1 year. In order to become 26 years of age, a demon has to wait for 41 years.
( apparent age - 23 ) * 975 / 23 = overall real age - 23
(biological age)
( 155 - 23 ) * 975 / 23 = 5595
5595 - 23 = 5572
The actual age of a demon right now in the year of 2245 is at the age of 5,572 years old, because they all age at the same rate after their 23rd year. This is because the main source of their lineage comes from one bloodline that is passed over generations, The Demon Grandfather, Khalfvyskov, who lived on Hetra long ago. He used a clock-based demon magic to set a vicarious life cycle for his future generations to come. That was how Demonization happened. Demonization is essentially hardcoded into every demon's future blood.