1. A phosphorescent light that hovers or flits over swampy ground at night, possibly caused by spontaneous combustion of gases emitted by rotting organic matter. Also called friar's lantern, jack-o'-lantern; Also called will-o'-the-wisp, wisp.
2. Something that misleads or deludes; an illusion.
Macgyver did something just like that on one of the episodes. He solved the mystery of "aliens" and these odd lights that would sometimes eminate in corn fields by recreating the whole thing. I'm guessing you're using the 2nd definition of ignis fatuus and not the first one from MacGyver. If you are using the 1st one, you get 2 more cool points.
More C4 please <3