Clearing the bookshelf, and only due to her tinkering nature, Aelia notices the tell-tale signs of a compression panel. Crudely done in her opinion, taking more space than necessary but did the job of appearing inconspicuous and hidden behind the books.

Pressing it, it folds down revealing a small space the size of a brick, empty except for a wide metal ring attached tightly to a bit of string that disappears into the wall.