Board Thread:General Discussion/@comment-71.60.21.82-20130121052227/@comment-108.84.156.64-20140731214038

easiest means of obtaining if siding with dawnguard... after returning serana to the vampires and getting ported out of the castle go back up the bridge to the castle gate, jump onto the railing on the right side of the gate (when facing). Use a wooden plate to "plate through" the wall connecting to the railing. This should put you behind the portcullis. Enter the castle. Everyone in the castle will be non-hostile. As long as you have at least a 40 in restoration you will be able to buy the spell. If you wait untill after serana meets back up with you at fort dawnguard you can still obtain but you will need to have "master of the mind" (as well as all related perks) and a high level calm spell as well as good timing, because the entire castle will be hostile and essential.