He'd had this job for several years now. From his position, you'd think that he'd worked extremely hard to get there.
You'd be wrong.
Sebastian was special, and not in the good way: he was around eight hundred years old, very much not human, and yet here he was, the king's personal advisor.
About twenty or so years ago, at this point he'd lost count, Sebastian met a young girl named Victoria. She was naïve and of course knew nothing of his origins. But she somehow trusted him, just enough for him to worm his way into her mind.
They courted for about three months before he impregnated her. She wasn't ready and neither was he, but for some reason he felt the need to tell her what would happen when she had her child.
So he let it slip that he was a demon, and that their child would be a demon spawn. By the next morning, Victoria and their child were gone.
Sebastian knew that there was nothing he could really do about it at this point. He could go searching for her but now that Victoria didn't trust him, there was a very slim chance that she'd give him the child or even get anywhere near them.
He decided instead to focus on another goal: taking over the kingdom, which was the original reason why he came to the surface world in the first place.
Sebastian worked his way into the palace and began small by using his magic to convince the lower guards that he belonged with them. After that, when the leaderships knew him well enough, he became one of them, and so forth.
He continued to gain trusts and worked his way up to the junior advisor position. Unfortunately, that advisor didn't trust him in the slightest. He'd finally hit a roadblock.
Instead of giving up, he simply killed the man, told the king that he'd died of a heart attack, and assumed to position naturally.
There was only a few more steps until his plan would be perfect.
Sebastian had watched Prince James grow up. He knew this boy was a hopeless romantic at heart, watching him play numerous instruments and charming the entire castle staff as he grew older. Little did James know that he was a pawn of his father's advisor.
Once James became of age, King Quentin would want him to get married right away. James's birthday was very soon and he knew there would be this terribly uncomfortable speech about how James needed to gain a wife so he could become king and she could sit beside him as his queen.
James would of course have no problems finding a suitable woman, and as castle advisor, Sebastian would be officiating the wedding. During the ceremony, he would slip a curse into the vows: the future queen would become barren and wouldn't be able to bear any children.
After the wedding, it most likely wouldn't be long until the happy couple would attempt to have an heir to the throne. Unfortunately, they would learn that it isn't possible. Instead, the two of them would grow old and once they die, the kingdom would be free for the taking.
But that would take far too long. Sebastian planned to pitch the king a plan that the king would agree to thanks to some magic: Sebastian is immortal, which the king doesn't currently know, but the magic would make that particular piece of information not much of an issue; because of his immortality, Sebastian would be the perfect king since he'd never die. His magic would be able to help the people, of course, and all would be well and good.
The king would agree and Sebastian would have the kingdom at his disposal. After this, he'd most likely kill the royal family, since they wouldn't really matter, and he'd take over the kingdom to turn it into his own little corner of hell on Earth.
Simple as that.
---
"Sebastian!"
He turned to see James hurtling down the hallway in a huff. "Yes, your Highness?"
"Where's my father? I have to talk with him." Oh dear, what's wrong now.
"I don't believe I know, your Highness, but you're more than welcome to come with me to find him."
"Sorry, no offense, but I most likely will be much faster on my own," James sighed before taking off again.
"No running in the halls, your Highness!" Sebastian shouted. James grumbled angrily but slowed down anyway. Hopefully this was something actually important and not some stupid thing that doesn't need the King's attention. He may be a demon, but unfortunately he still had a job to do: protect the king and make sure that he isn't bothered.
Reluctantly, he followed James to the King's quarters.