When magical practitioners have achieved absolute mastery of multiple disciplines in magic they can perform a ritual to obtain immortality and godhood. It's a very dangerous ritual that usually kills those who perform it. Those that don't immediately die usually quickly go insane and never obtain their power. For those that succeed there are still consequences since the new magical power, if not combined with the continued cultivation of one's self, will slowly consume their souls and thus blunt any magical achievement that would fulfill their potential. However, because the loss is gradual it's usually not noticed. And by the time most of the soul is consumed there isn't enough soul left to want to get it back.
This is why deities were so often narcissistic, cruel and dishonest. In the process of obtaining their godhood they'd lost the finite and fundamental nature to themselves that enabled them to care for others and show compassion without it having an ulterior motive. They demanded worship not understanding that anything truly worthy of praise would never demand it in such a fashion. They would justify and excuse their cruelty while doling out harsh punishment to those they felt slighted by.
Nyx had definitely followed this path. She sought to obtain divinity in order to change the natural order of things and create a kinder world that she longed to live in, but when she obtained it she lost herself and the change she wanted to make soon felt hollow and meaningless until she lost her motivation. The Fae King wholly despised deities and those who tried to obtain divinity. He didn't understand the allure of the infinite being himself an immortal creature. He also didn't understand the need for power being inherently magical.
The ritual to obtain divinity is quite complex, but culminates with the absorption of a cocktail of herbs and magical elements often referred to as ether. It was commonly thought to be so named because those that didn't die from it would still pass out similar to how people would react to the chemical by the same name. However, many scholars contested that opinion insisting it was the other way around as the ancient tradition was older than chemistry.
Distilling was very complex and difficult. The means to obtain all the ingredients were often far more than a king's ransom. Many who obtained it would attempt to pass it on to their children, but this just as often ended in failure. As time passed there were more and more attempts to cheat or subvert this ritual with disastrous results. This resulted in a ban on many of the ingredients and restrictions on who could perform the ritual which was often also prohibitively expensive. The Fae King would not allow it at all anywhere in his realm.
Nyx was aware of this when she performed the ritual. Moreover, she had lied, cheated and stolen to obtain the elements. This was out of her normal character, but she was desperate.
The realm of the Fae is inherently magical, so it was ideal for the ritual. She knew she couldn't hide forever what she'd done, she just needed to hide it long enough to complete the ritual. After this the Fae King found out and this is where the animosity between the two started.
Over the years lots of things transpired. The insanity had set in to Nyx who couldn't even remember who she once was. Even her perceptions of reality were warped as she drifted in and out of delusion. Her magic was also out of control. Without her knowledge she both cursed and blessed. She lied without intention and told the truth attempting to lie.
And now she was trapped, yet again, by magic she could no longer see nor understand because she had become crazy from the magic she already possessed, but maybe it was more accurate that the magic had possessed her. She couldn't do much in her current form, but maybe she could manipulate someone who could.
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"I never pegged you for Zion's lap dog, I thought that was Cerberus." Nyx appeared before Contessa.
"Says the faithful favorite finch of the Fae King? I honestly don't know what purpose Zion has for you, but getting to know you now I'm sure it's something stupid. I know somewhere in Zion's mangled, and artificially preserved soul they probably feel some kind of pity for you, but I don't. I don't have a heart or a soul, so you can try to win someone else over with your unkindness." Contessa retorted.
"Whatever Zion's giving you, I'll double it." Nyx replied.
"That's not something you can give. I have been alive through many ages. I have wealth and power. The only thing that vexes me these days is boredom, and I'm already bored with this conversation...and possibly your face." Contessa said mockingly.
Zion's fairy companion appeared suddenly having stayed invisible since the contract she had signed in the woods and piped up. "Contessa, who are you talking to?"