This is cool. I created a campaign once but it wasn't nearly as detailed and in depth as this. I have quite a few ideas to offer, first of which is a talking, intelligent ogre named Arthur. There is a secretive group of evil necromancers that I creatively named the Deathlords. In an attempt to perfect an advanced mind control spell they performed experiments between a man named Arthur and an ogre they had held captive. One of the experiments went wrong, and the minds of the ogre and the man were switched. In a mad fit of rage, Arthur broke free in his newfound body and escaped with the mind control research, killing some of his captors along the way. The ogre in the human body, however, was powerless, and the Deathlords kill it so that Arthur would not be able to get his old body back. He now lives alone in the mountains, keeping away from civilization and guarding the Deathlords' mind control research. The connection to the campaign was that there would be an ogre sighting that the players could investigate to start a quest. They would then meet Arthur who asks them to kill the remaining Deathlords in their fortress in exchange for the mind control research. The players would then confront the Deathlords (there are 3 of them, each more powerful than the last) and loot the place. Then they would be awarded the research. After that, once during each long rest, a spell caster in the group could roll a d20 to decipher the research and, if a number above 15 is achieved, obtain a version of the mind control spell any spell caster could use. However, I took the liberty of limiting its use to once per session so it wasn't rediculously overpowered.