The Tritone Chord - The Devil's Chord

Historically, the tritone chord was noted as being vivacious and forceful in assent. In this arrangement, the four and five of a major scale are played along with the root. It's just devilishly difficult to get a choir to perform it. If you really want something to appear darker or spookier, more so than a minor key, you should really consider using different modes. But that's probably more music theory than your average stuffed billier mind listener is ready for.