Originally Posted by Zero1986

Well of course the devil himself didn't actually create them. The Devils's Chords, or tritones as they are more technically known, are sets of notes that were seen in the middle-ages as too dark, evil and menacing for music and therefore they were associated with the devil. Musicians who used these were often punished by the church or excommunicated. Examples of tritones are B-flat-E, F-B, B-F, A-D-flat and many others.
Listen to 'Black Sabbath' by Black Sabbath for perfect examples.