A Swamp Wisp is a spirit or sprite of the swamps that keep the Swamp clean for King Mudge.
Background[]
Swamp wisps pollinate flowers, drink honeydew, and annoy frogs. Of most import they collect and enjoy hearing juicy secrets. They avoid the Swamp Witch's Cove since she was especially nasty since the tempest. The Witch's poisonous water makes them ill. They promised to give Connor an antidote for the poisonous swamp water in trade for a juicy secret. Connor received a incredible secret from the Whispering Weeds which proved to be astonishing to the Swamp Wisps. In reward they gave him a blossom that would protect him from poisonous water. They then told him to search out for King Mudge. They couldn't wait until he heard the secret Connor told them. They had a secret for Connor, they told him to find the Golden Ladle, and that it could cleanse the poisonous waters. They required no more secrets, so Connor left them.
Behind the scenes[]
Swamp wisps are nature spirits or sprites. They appear to be more elemental in nature than undead or a corporeal creature. They are referred to as sprites in the KQ8 Hintbook, and elements of their story are akin to mythic ideas of small sprite fairies. In some traditions wisps or will-o'the wisps are associated with fairies or fairy fire rather than being necessarily undead ghosts.
Swamp sprites/wisps appear to have a similar appearance to the ice sprites mentioned in King's Quest: Kingdom of Sorrow, a small race that appear as flying ice crystals. This may of course be due to the fact that they are moving so fast that average eye cannot see them, but only the dust and sparkles that they release.