Black Angel was a 25 minute short film, directed by Roger Christian (with financial help from George Lucas) that played before old showings of The Empire Strikes Back (in Europe and Australia anyway). It has been lost for years (with Christian even having trouble locating the film's negatives), and subsequently was not released on other mediums, until recently.
Black Angel was a fantasy film in which a knight needed to rescue a princess from a Black Knight. While that story sounds simplistic, I'm sure it has several different layers of ingenuity and character hidden beneath its naive facade (much like Star Wars), and above all else most likely looks fantastic. Last December, someone at Universal Studios discovered a Black Angel print, and now Christian is left deciding how the film's going to be released. I'm hoping for something I can see right away. All this anticipation is killing me.