In Skin Game Harry talks about spending some time figuring out what the island and prison can do. He mentions that he could now shut down a threat like the one presented to the island/prison in Cold Days. I would love to have some more info on what he found out. Did he get more history of the island, what additional defenses does the island have, are there any perks to being the Warden, are there any other side effects to the sanctum invocation, and as other have mentioned, does he have access to a list of prisoners? Unfortunately, we probably will not find out more about Demonreach for several books since Harry has moved back to Chicago. I wouldn't be surprised if Demonreach does not appear again in a significant way until the BAT.