"Hinkypunks are one of the obstacles that Professor Lupin sets for the Defense Against the Dark Arts exam."
From the Story
Discovered in Book 3, Chapter 16, Professor Trelawney's Prediction
"Hinkypunks are little one-legged creatures which seem to made of wisps of smoke. Although frail and rather harmless-looking they mislead travellers by luring them into bogs with the lamps that they carry."