Between Jess and Hewitt you manage to learn the following:
1. There is, like, a dozen of spells and effects on this tower, some of them linked together and most of them well above your pay grade. Nothing seem to be immediately harmful given that you are still alive, but for example you cannot sense any auras behind the double doors leading north, even though you well expect there should be some. You check it with the front doors and yep, your divinations are blocked by these too, so there is apparently some protective magic at work (well, or some lead hidden inside the doors, you might try disassembling the doors to check the hypothesis).
2. While a multitude of high-level auras like this is certainly not something you see every day, some stuff is quite recognizable, if noticiably permanent:
2.1 Illumination on the ceiling, which is a version of Light.
2.2 The illusory walls, which use the same version of Silent Image.
3. Apart from the tower itself, there are some more localized auras:
3.1 Two circles of silvery metal set into the floor in the corners of the rooms (or are they better considered parts of the same room) behind the illusory walls. These shine moderate Transmutation.
3.2 Two tridents the fishmen were attacking you with. These are +1 tridents.

Laurelata, meanwhile, both hears and later sees something interesting:
4. She hears some faint activity behind the doors leading north. People moving and talking? She does not recognize anything said.
5. Then she no longer hears this activity.
6. Then she notices what seems to be a keyhole in the wall to the left of those double doors. Noticiably, it does not seem positioned like a door lock normally would be.