Here is a chess riddle for you: Which piece belongs to only one player, possesses the most powerful transport abilities yet has the weakest value?

That piece, "the Black Ghost," belongs to Ralph Betza's eponymously named chess variant.

Its power derives from its ability to teleport itself to any vacant space on the chess board on any given move. But it is weak because, though it can be captured, it does not possess the ability to capture.

Why do the Black pieces include this Ghost piece and the White pieces do not? The Black Ghost was created as a way of offsetting White's supposed first move advantage. Whether the Black Ghost achieves this purpose is an unsolved problem. Possibly, in this variant, it's the black pieces that have the advantage. Another unsolved problem involving the Black Ghost is whether a Black Ghost with King can draw against a rook with king in the endgame.

If it can't capture other pieces, what good is it?

The Black Ghost may have the most value in the endgame when it can be used to block an opponent's pawn from queening or to pick up an all-important endgame tempo (many endgames hinge on creating zugzwang situations), sometimes converting close endgames from losses into draws or from draws into wins. It may be worth noting however that a Black Ghost's presence might make achieving certain types of stalemates impossible.

Where, on the chessboard, does the Black Ghost lie at the start of a game? Fearing the Black Ghost might have too much power for its intended purpose, Betza recommends placing it in front of one of the key developing squares in the opening, f6, e6, d6, c6, to weaken the Black pieces by stymying their opening development. How this originating square should be decided Betza does not address. Perhaps the player with the white pieces should decide where the Black Ghost should begin as part of his/her first move.

The Black Ghost can be used as an obstacle to an opponent's development or as part of a sacrificial combination or to seize and maintain a square or to protect a piece by placing itself as a suicidal barrier confronting the attacking piece. Betza considers the Black Ghost to be worth less than a pawn, though almost as much. This may give an opposing player pause before exchanging anything for it. Problems have been reported with Zillions of Games' ability to interpret the value of the Black Ghost, tending to award it approximately the value of a Queen probably because of its movement capabilities.

An alternate proposed name for the Black Ghost is "Servus" which is Latin for serf. Note that "pawn" is Latin for footsoldier.

Other pieces sharing this weakness of being capturable without being able to capture include James Spratt's Princess and Imperial Princess in Imperial Chess. Yet, weaker pieces exist than these, pieces which lend their strength to opposing pieces, pieces with so-called "Negative Values". See Rhubarb, Rutabaga, Negative Relay Knight and Ruthven. Contrast this with the Mamra which can only be captured by pawns but not by pieces. Or superpowerful pieces such as the neutral Juggernaut and the Behemoth which can't be captured. Mythical Fantasy Conquest has a Protector, a piece that can neither capture nor be captured.

Another uncapturable but highly familiar piece is the King (ironically referred to as "Royal King" to denote its vulnerability; a "Non-Royal King" could be captured without losing the game -- see Man).

See Also:

Behemoth Chess By Donald Seagraves

The Black Ghost by Ralph Betza

Imperial Chess by James Spratt

Juggernaut Chess by Seth McGinnis and Erik Wilson

Mamra Chess by George Tsavdaris

Mythical Fantasy Conquest or Mythico Fantasio by Lim Ther Peng

About Negative Pieces: Worse than Worthless by Ralph Betza