Ignis fatuus : A phosphorescent light that appears, in the night, over marshy ground, supposed to be occasioned by the decomposition of animal or vegetable substances, or by some inflammable gas; -- popularly called also Will-with-the-wisp, or Will-o'-the-wisp, and Jack-with-a-lantern, or Jack-o'-lantern.

Ignis fatuus : Fig.: A misleading influence; a decoy.

Example:


Taxonomy
will-o'-the-wisp, wisp, lantern, fire, ghost, treasure, Folklore, phenomenon, ignis fatuus, will-o, Will o' the Wisp, travellers, the-wisps, ball, spirit, flame, graveyards, candles.

Defination from the web:
Ignis Fatuus was not always considered dangerous. ... "Ignis Fatuus" is found in Charlotte Brontë's Jane Eyre in chapter 22, and 28 when she is lost in the moor. ...