Will-O'-Wisp
What is your strategy for confronting the fantasy creature Will-O'-Wisp in Dungeons & Dragons?
More info on this creature: Source 9
All I can say is ranged weapons, besides that melee ones. You don't want to be pulled in by these baddies but they are not really tough as far as hp. Land a few nasty blows and you should make it.
That said these monsters unused in conjunction with crocodiles or something similar would be most deadly.