(Spoilers, obviously)

I'm in the Plane of Unlife and am doing the Necronomicon quest. However I accidentally already killed the ghost king WITHOUT using the blade of the fathers, and afterward I found the prince and talked to him, but since I didn't kill the king with the sword I think I screwed everything up. Is there any way to fix this? (And no I don't have an earlier save)

Bump. I don't believe I'm the only one to ever have this problem.

You can either

• Go open Midas with the construction set and modify the quest script. It is very fun, and very easy to do.
  
• Go http://www.uesp.net/wiki/Oblivion:Console and look for something useful.
  
  • If the body has not disappeared, you may use this command directly (What command? You find it!)
    
  • If the body has disappeared, you have to enable the corpse.
    
    • In order to enable the corpse, you need to find the King's ID. Yay! You'll probably need the construction set again!
• Since the point of the quest is to get a damned book, you can open up the construction set (:o) and look for the Necromdfgdfgdf. And add it to the game using the console command. Completion of the quest is not really important.After you get the book, you can delete it from your quest list.
  
• You can also look for the key that opens the door to get the book in the construction set.
  
• Finally, the hardest, most insane solution, would be to "unlock" the door using the console to the room that holds the book. Then delete the quest from your quest list. The room should be in the back of the throne room.
  
• Equally as difficult, the room should also be in the same cell a the throne room, "phase" your way through the door using a console command...

I recommend that whatever path you take, to kill whoever gave you the quest to end the cycle of death
*Hint* Do one of the two last options.