For weary, tired travellers, especially those fearing they may have got lost, there is little that can inspire more hope than the sighting of a light – especially come night-time. It is not surprising, then, that myths about the will-o’-the-wisp have sprung all over the world, from Europe and Asia to the Americas.

In Scottish folklore, will-o’-the-wisps are variously depicted either as mischievous spirits (typically fairies), or even the ghosts of the dead, eager to lead travellers off their path and into their death. The lights typically appear close to a bog, marsh, or swamp, places where straying off the beaten path can become dangerous – or even deadly.

Most of the myths associated with the will-o’-the-wisps (known in Latin as ignis fatuus, “foolish fire”) show a malevolent, mischievous, even outright cruel creature. Few myths, however, show the will-o’-the-wisps leading those brave enough to follow the light in the middle of the dark night to a vast treasure, and riches beyond comprehension.

Some believe that the spirits behind the will-o’-the-wisps were souls who could enter neither Heaven nor Hell, and were thus forced to wander the earth forever. Others think the Devil himself was behind those attacks, instructing spirits to return to earth with the sole purpose of leading others astray. For yet others, the will-o’-the-wisps had a function similar to that of a banshee, becoming an omen of an upcoming tragedy. Uniquely, in Sweden, the will-o’-the-wisp is a manifestation of an unbaptised soul, who tries to lead travellers into bodies of water, in hopes of being baptised.

Opposing folkloric and superstitious traditions, science suggests that the will-o’-the-wisps, and the lights produced by them, are a result of the oxidation of methane, diphosphane, and phosphine, a process resulting from the decay of organic matter.