



TL;DR
Abbadon is a demon, borne of a high-class demon and a demon who's lived in the human world for years, and helped them with various monster problems. The young demon learned swordsmanship from his father, and magic from his mother.
Upon eventually setting out to explore, he went to the demon realm only to discover that they were incredibly racist and narrow-minded, so in annoyance, Abbadon made it his goal to take the throne and change it all.
To do so, he needs servants, people or creatures recruited into his familia to help him fight, as well as support him, to which he'd support in kind. Several are needed, so this quest may take some time.
First Members

Actually older than Abbadon, despite her apperance, and fairly knowledgable about the world and it's creatures. She's also something like his healer, just as often found patching him up and scolding him as she is supporting him and Belrog in combat.

Abbadon's faithful cainine companion. This special pup has been with the boy since he was a child, and refused to leave Abbadon's side when he set out for adventure.
Abbadon Demus
Abbadon's story is fairly unique as far as a demon stories go. With a demon for a mother who grew up in the demon realm, and a father that lives in the middle (human) realm, that can happen. Especially when they're both quite powerful. But that's a story for another day.
Abbadon himself was raised more by his father than his mother, and it shows in his swordplay. His father was a well-known monster-hunter, known for having been able to slay even some of the most powerful and largest of fierce beasts, and even demons on occasion.. He was only able to because of the fact he was a demon himself though, though few knew that about him. He'd been in the middle realm for years.
His mother was a high-class demon of the demon realm. Considered untouchable by most, it infuriated everyone, including the demon king, that she would lay with a human man, powerful or not, and not one of her own kind. All thought that another high-class demon would have been a much better suitor.
So she gathered her servants and left, to join Abbadon and his father. By this point, the grey-haired boy was about eight or so. He already knew how to handle a sword, and could manage a little of his magic. That changed quickly. Now that both of his parents were around him, the child lived happily for several years, learning a variety of skills from woodcrafting to forging to magic to swordsmanship. They passed on all they knew.
And once Abbadon was a bit older, they told him why they were hidden away, and what he was. The child had already figured half of it out, and the rest didn't surprise him. Your mother having horns and pointed ears, and your dad being able to hurl boulders at monsters was a bit of a giveaway after all. Plus, he had a dog made of fire. Not normal in the world, from what he'd observed.
So years passed, and once he was of age, Abbadon decided to set off and explore. His first stop would be the demon realm. He'd heard stories, but he'd never been there. He wanted to know about the realm of which his species came from.
When he arrived, he was surprised at how much it was like the middle realm. The sky was always clouded by deep red clouds, but that was about the only major difference. Well, that and the wildlife. There was no sun, but everything was always visible, even if slightly dimmer than the middle realm.
But one other thing surprised him. The demons there were racist, and seemed to look at him like he was dirt. They thought that he was below them, since he was raised in the middle realm. He proved them wrong quickly, as soon as an opportunity presented itself. A single demon of high standing spat at the teenager. This rubbed the young demon the wrong way, and a fight ensued.
That demon barely escaped with his life, and Abbadon was perfectly fine. This surprised Abbadon as much as it did the demons though. He'd always compared his strength to that of his father, and he'd always been physically weaker than him, even if he was faster. He had known that his father was a demon, but he had no idea that he had been so much stronger than a high demon.
However, this display of power did not sit well with any of the demons, and they refused to acknowledge some young upstart as truly one of them, even if he WAS a high demon. So the young man set off to prove all of them wrong, out of spite. He'd take the throne, and make them rethink everything they thought they knew. But over time, this goal evolved.
But first, he'd need servants. What are servants? They are creatures added to the demon's familia. They could be anything, from a dog, to a human, another demon, or even to a dragon if one could be found. By becoming a servant, that being's power is increased, and so is the demon's in turn. Because of this, demons often strive to find powerful servants, as their power is increased even more. On top of that, the amount of power gained can be increased even further as stronger bonds are formed between master and servant.
This isn't a system that demons devised, actually. It's something they were born with. Through forming a 'master-servant pact' the demon's familia is expanded. But this is also an indicator of a demon's social standing. If a demon has powerful servants, or has many servants, or especially many powerful servants, the higher their social standing. Of course, they have to be able to properly manage them.
Abbadon, however, is searching for servants for a multitude of reasons. The first being, he isn't fond of being alone. He was a social creature, and he'd be much happier sharing in his adventures. The second being, he knows that he isn't strong enough on his own to fight the demon king. Even if he is as powerful as the man himself (which he is) he would still have to deal with the servants at the same time, which he can't do. The third and final reason being is that he hates being disrespected, so if he can collect a number of servants that he can trust, even the higher-class demons would have to respect him.
And such began his quest to change the Demon Realm. He knows from experience that demons aren't evil creatures by nature. His parents proved that. As time pased, he did eventually collect a few servants that he trusts greatly. Their loyalty to him is without fault, and if Abbadon is somewhere, so are they. They are always near him some way or another.
Maybe you'd like to join him?