This is an AWSOME way to get your destruction skill to 100! Its a bit of a grind. took about an hour for 15-20 levels in destruction.
To get here you have to have completed the Dark Brotherhood quests. After you complete them you can buy things for the dawnstar shrine. One of them is the torture room. Filled with fresh meat.
You can see in my video that the process is that you have to lay down frost runes or fire whichever to damage the torturee to NEAR death....but then heal them back up with healing hands spell. RINSE AND REPEAT.
Now the old lady im abusing in the vids is the best contestant in here. She is the only one who regenerates health a bit. So just use her and ignore the others.