It's a large stone bowl that you can use to hold memories. It's good if you've got too much in your head and you want a little perspective.

[ Or if you're a spy and need to pull a few traitorous thoughts out. ]

I've had a fair bit of training in how to stop other people from entering my memories and that included the reverse, but that can be a bit invasive. I spoke with Linn, my companion, and a great witch, and we can sort of mingle what I know from my world with how magic works here and do this safely.