A Will-o'-the-Wisp is a phenomenon often seen in marshy or swampy areas, where it appears as a flickering light. This mysterious glow is typically blue or green and is caused by the combustion of gases released from decaying organic matter. People have historically associated these lights with folklore and superstition, believing they to be spirits or fairies. In scientific terms, the lights are usually attributed to methane and other gases igniting spontaneously. While they can be captivating, Will-o'-the-Wisps can also mislead travelers, causing them to wander off paths in search of the elusive light.