Merlin knew what was coming; he had planned for just this thing. It hadn't even been difficult to arrange. The best part was that no one knew, or would ever know.
When Sir Ulfias came searching for Merlin, as the wizard had known he would, Merlin was only too happy to go with the knight (though he made sure the knight did not see his glee).
When Merlin was ushered into the presence of King Uther Pendragon, he hid his cunning behind the façade of the kind, grandfatherly figure that most people expected out of an old man.
"Welcome, Merlin," the King said. Uther was a tall, handsome man, and arrogance radiated off of him in waves. Such a man was easy to manipulate.
"I know what it is you desire," Merlin said. "If you will be sworn to me, to fulfill my wish, then I will give you what you desire." It didn't matter to Merlin that what Uther wanted was an unholy sin. Merlin would grant this wish, because it would fulfill Merlin's own.
"I swear by the four Evangelists to grant your wish if you can fulfill mine," King Uther said.
Merlin almost laughed at the delicious irony; Uther swore a Christian oath in order to have one night with another man's wife.
"Here is the payment I would request," Merlin said. "The first night that you lay with the Lady Igraine, you shall get her with child. When that child is born you will deliver him to me to be raised as I see fit."
"So be it," the King said, without a moment's hesitation. He was so eager to be with the Lady Igraine he was willing to sell his firstborn child. If Merlin had asked for Uther's soul, he'd probably have agreed to that. Not that Merlin would have asked for Uther's soul; future kings that Merlin could manipulate and control were so much more useful.
"Very well then," Merlin said with a kind smile. "Tonight you will lie with Lady Igraine in the castle of Tintagel. I will disguise you to look like the Duke her husband, and I shall disguise Sir Ulfius and myself to look like two of the Duke's knights. You can stay with her all night until I come for you in the morning."
King Uther leered, obviously planning the things he would do to Lady Igraine this night. If Merlin was any sort of judge, Igraine was in for a rough night.
"Let's be on our way then," King Uther said.
They saddled up three horses and left the camp that surrounded the castle Terrabil, where the Duke had placed himself. It amused Merlin to know that the Duke had sent his wife away to Tintagel in order to keep her safe from the fighting, but this very act in an attempt to keep her safe was what would leave her open to be taken by King Uther.
To make sure his plans would come about the way he wished, Merlin used a bit of his magic to get the Duke's notice; the Duke loved his wife too much to not be alarmed by the sight of knights from Uther's camp heading to her castle. He would attack Uther's camp, and if Merlin's magic worked (it always did) then the Duke would be slain in the ensuing battle.
Merlin had their disguise well in place by the time they arrived at Tintagel. Lady Igraine came to greet King Uther, whom she thought was her husband. Igraine was indeed a beautiful woman, with long blond hair, smooth skin, large breasts, and a soft, soothing voice. It was no wonder that Uther lusted after her so much.
Merlin whispered another spell as Igraine led Uther to her bed chamber, one to ensure that Igraine would get pregnant this night.
Merlin settled back against the wall, pleased with a job well done. He would have Uther's son, his puppet King, and Merlin would rule all of England through him.
Laughing to himself, Merlin said, "Long live King Arthur."
AN-So, I was reading Le Morte Darthur by Sir Thomas Malory for one of my college classes, and this is seriously how King Arthur's conception happened. Which made me think, there is no way Merlin is a nice character. No way at all. Hence this one shot, exploring what I feel Merlin was thinking throughout this whole episode.
Might I also mention that the whole reason Uther attacked the Duke in the first place was because Igraine refused to have an affair with him? Yeah, seriously. Not nice people. At all.