World Eaters 'How To' for exploiting the loophole in Khorne's 'No Being a Sorcerer' policy:
1. Collect loyalist Librarian.
2. Put him in the warp until he goes 'Event Horizon'
3. Collect your new sorcerer and point him at whoever you are angry with at the moment.
Note: You will need to keep a close watch on your sorcerer as he will likely be a tad unpredictable.
Of course I'm going to be completely unable to run this guy in my Butcherhorde or any other dedicated Khorne detachment but he could always make an appearance in a CAD at some point.