Pensieve

A Pensieve is a shallow basin of stone or metal, cut with runes and strange symbols and set with precious stones, which holds memories drawn out of a person's head. What lies in it is neither quite liquid nor quite gas, a silvery cloud that shifts without stopping and gives off a whitish light. A witch or wizard who lowers their face into the basin falls into the memory and stands inside a scene from the past, watching it happen from the outside without being able to touch or change any part of it. Sorting and examining thoughts this way is harder still, and very few wizards can manage it, which is part of why so few ever keep one.