Vesper

-Queen of the Abyssal Demon, a water-based demon said to be born from the very depths of the ocean the moment a Deity called it its home.

-Having their territory close to the Magma Demons for the longest time, the two sub-species shared an extreme hatred and rivalry, which only increased as the magma would continuously expands itself and slowly dry the lands of the Watery demons. The sub-species would almost turn extinct because of this.

-Soon, an event in the name of Hell Breach, in which the Gates of Hell opened letting any demons escape and wander the Earth would mark the perfect occasion for a revenge, the abyssal Demons using the chaos as an opportunity to strike, killing almost every one of their ennemy in the process.

-The few who escaped only doomed themselves the moment they arrived on Earth, ending up getting killed by humans.

-The only one remaining was a beautiful maiden in the name of Eleanor, who had to face the person responsible for the death of her pairs, Vesper.

-While Vesper only did this for the sake of her people, she could not bring herself to kill the girl only because of who she was. So instead, she decided to take her with her and protect her.

-Years later, the two are extremely close, like sister, Vesper giving Eleanor the freedom to do anything.

-Overall, Vesper hasn't been seen by much, the only time she showed herself the longest was during the war between their nemesis. She's highly respected and powerful, demons outside of the Kingdom considering her mysterious, like an enigma.

-Eleanor often speaks in her name and represents her because of that. Truth is, there might be a twist in which Vesper is ill and can hardly move from her castle.

-Her design could take some inspiration from some Abyssal creatures but I'm not quite sure what yet.