Anything, really. I would dearly love to be able to visit it any time I wish, but I have to admit that the chances are probably slim, unless he no longer has access to it or his access is otherwise weakened. I can only imagine what sort of information might be held upon those shelves. Histories, magicks, legends...

[ He's. He's a nerd. He could live in a library. He wanted to go back into a tower that tried to kill them. This is not abnormal. ]

Though I am particularly interested in finding ways that might help us to defeat him. I am no stranger to researching hostile deities. Provided we can reach the library and can hold a stable pathway to it, I will be in my element.