Dwaallichtjes (translation: Wandering Lights) are ghostly apparitions that appear at night. Other names for them are Dwaaslichtjes, Droglichtjes, Alflichtjes and Valse Lantaarns. In the region of Groningen they were commonly known as Hiplichtjes, Glende Kerels, Gloeiende Kerels, Stallichtjes, Stalkeerse or Stalkaarsen. Friesland spoke of Nachtlampken, Spoekljochten, Dwylljochten or Dwaalljochten. Flanders knew them as Dwoalluchtn of Dwoasluchtn. These will-'o-the-wisps are often blue in hue, and mostly seen in swamps, graveyards and above bodies of water. Sometimes they appear as transparent figures with a luminous lantern. The wandering lights are also said to excrete some sort of residue (ectoplasm?). One could rub this substance over their body in order to become invisible.
Said to be the spirits of criminals, they are known to frequent crime scenes or the locations of future houses, canals or (rail) roads. Tales about the wandering lights implied they might indicate hidden treasure. Some people believed they were elves playing tricks with their minds. Those who decided to follow the lights, risked getting lost. Or worse: they'd be led into danger. The lights have been known to lure people into the swamp. Again others say the wandering lights are spirits of unbaptized children. One could lift them from their curse through baptism, though it's been said to attract more such spirits. It's an activity that could last until morning sunlight.