In the context of spontaneous case investigations, a vigil is a period of sustained observation or watchfulness during which researchers aim to witness and document paranormal activity, typically conducted in reputedly haunted locations.

The setting for a vigil is often chosen based on historical significance, reported supernatural events, or anecdotal evidence suggesting paranormal activity. These sessions are often held in the dark, as many believe that reduced lighting enhances the sensitivity of human senses. There's some truth in this, our hearing might become more acute in the dark, but often at the cost of completely eliminating what is arguably our most useful sense, sight.

During the vigil, investigators often "call out," speaking aloud to address any spirits present and encouraging them to interact, either by showing themselves, making a sound, or interacting with the many different types of ghost hunting equipment available. However, not all of these devices are as robust and...