Avilia Graymore

 is known as the First Demon Lord, she is a Demon of Sin.

Appearance
A beautiful and fair young lady. Her hair was a silky smooth purple that had an ominous glow and fell down to her bosom. Out of the top of her head emerged two, sharp devil-like purple horns that looked similar to his own only much longer with some demonic runic writing written on them. She had bright purple eyes that had nearly exactly the same look as his eyes of sin, only with a much more complex structure and a brighter glow, including the red pupils in her eyes. Her luscious red lips, long eyelashes, and relatively thick eyebrows emphasized the beauty of her face and the rest of her features such as her clear, slightly pale skin.

From underneath her face laid a golden necklace around her neck that looked identical to the one that he used to wear before it was crushed. The only difference was that it did not have his family motto engraved on it like he remembered.

Even further below she wore a magnificent set of tight, slightly revealing armour, more intimidating than any set of armour he had ever laid eyes upon before in his life. It was a mostly black and purple set of heavy metal looking armour that had demonic engraving and patterns all over it with skull-like shoulder pads. Due to it being so tight, it was very clear to see and admire her hourglass figure with a narrow waist and wide hips, it also made it easier to see how big and voluptuous her breasts were that were nearly bursting out of her armour.

From her back were a pair of purple and black demon wings that spanned over 2 meters in length that looked dangerous yet still had a level of elegance and beauty to them.

Background
At the start of the story she was inside Moby's golden necklace given by his parents.

After her death she put her soul into the necklace to help choose and train the future Demon Lord. That necklace somehow appeared in Moby's family and in the end was passed down to him.

In chapter 5, after the necklace absorbed enough negative emotions and was broken by Nathan the soul went inside Moby.

choose to act like a system because after looking at the world she found a lot of people laying video games and thought it would be a easy way to train a future Demon Lord.

She was crowned as the first-ever Demon Lord of the netherworld at the age of 1928 after signing the treaty to end the Great Seraphodemon War.