Unicorn Great Chess

The innovative Pawn structure of Great Chess allowed each side to have 22 pieces on a 10x10 board, including two (R+N) pieces, a (B+N) piece, and a (Q+N) piece. Unicorn Chess, my entry in the 100 Squares Contest, replaced the (B+N) and (Q+N) pieces with two Unicorns and changed the initial setup. Unicorn Great Chess removes one Chancellor and one Unicorn from each side, adding a pair of Lions (on the second and ninth ranks). The Lion is identical to Ralph Betza's Half-Duck (HFD).

Setup

      a   b   c   d   e   f   g   h   i   j
    +---+---+---+---+---+---+---+---+---+---+
  0 | c |:r:| n |:b:| u |:k:| b |:n:| r |:q:| 0
    +---+---+---+---+---+---+---+---+---+---+
  9 |:p:| p |:p:| p |:l:| l |:p:| p |:p:| p | 9
    +---+---+---+---+---+---+---+---+---+---+
  8 |   |:::|   |:::| p |:p:|   |:::|   |:::| 8
    +---+---+---+---+---+---+---+---+---+---+
  7 |:::|   |:::|   |:::|   |:::|   |:::|   | 7
    +---+---+---+---+---+---+---+---+---+---+
  6 |   |:::|   |:::|   |:::|   |:::|   |:::| 6
    +---+---+---+---+---+---+---+---+---+---+
  5 |:::|   |:::|   |:::|   |:::|   |:::|   | 5
    +---+---+---+---+---+---+---+---+---+---+
  4 |   |:::|   |:::|   |:::|   |:::|   |:::| 4
    +---+---+---+---+---+---+---+---+---+---+
  3 |:::|   |:::|   |:P:| P |:::|   |:::|   | 3
    +---+---+---+---+---+---+---+---+---+---+
  2 | P |:P:| P |:P:| L |:L:| P |:P:| P |:P:| 2
    +---+---+---+---+---+---+---+---+---+---+
  1 |:C:| R |:N:| B |:U:| K |:B:| N |:R:| Q | 1
    +---+---+---+---+---+---+---+---+---+---+
      a   b   c   d   e   f   g   h   i   j

Pieces

With exceptions noted below, all usual Chess pieces are the same as in Chess. Additional pieces are described below.

The King moves as the King in Chess. It castles by moving two spaces toward the Rook, with the Rook moving to the space the King passed over. The usual castling restrictions from Chess apply.

The Unicorn moves as a Bishop or a Nightrider. A Nightrider can make consecutive Knight moves in the same direction, until it makes a capture, is blocked by another of the player's own pieces, or has gone as far as the board will let it. The Nightrider move can be blocked only on the spaces it would land on with a Knight move. Any of its Knight moves can leap over pieces as a Knight would.

The Chancellor moves as a Knight or a Rook. Placing Chancellors and Queens in the corners (with the Pawns in front of them also defended by Knights) is an opening setup I have used on 64, 80, and 100 squares.

The Lion is Ralph Betza's "Half-Duck" (HFD, a piece that can move one square diagonally or jump two or three squares orthogonally), from the Remarkable Rookies army. I chose the name Lion as a reminder of the Lion in Grande Acedrex (a 3-square leaper, according to some accounts). That game also has a piece called the Unicorn (or Rhinoceros).

Any Pawn may make a double move from any space a Pawn of its color starts on. So, for example, if the d2 Pawn moves to e3 by making a capture, it may make a double move from e3. Whenever a double move take a Pawn to a space horizontally adjacent to an enemy Pawn, the enemy Pawn may take it "en passant" on the next turn. On reaching the last rank, a Pawn promotes to a Chancellor, Queen, or Unicorn of the same color, but not to any lesser piece.

Rules

Most of the rules are covered under the piece descriptions. Checkmate is a win and stalemate is a draw, as usual.

P=100, N=300, B=350, L=500, R=550, C=900, Q=1000 and U=1000

are suggested values (definitely not rules). The Queen should be halfway between [Rook plus Bishop] and [a pair of Rooks] on any square board. The Chancellor seems to me to be worth [Rook plus Knight plus half of a Pawn]. It is difficult to compare these two pieces directly, so I am going to introduce some new pieces. The "Elephant" moves like a Ferz or an Alfil, and is worth 100 points less than a Bishop. The "Grand Rook" moves like a Rook or an Elephant, and is worth 100 points less than a Queen. The Grand Rook and the Chancellor are similar in design, so I would expect them to have the same value on any square board.

Notes

Combination pieces including the Nightrider (NN) are rarely used. Arno von Wilpert allows Pawns to promote to Elephants (Q+NN) in his 8x10 variant Wolf Chess (1943). G. P. Jelliss uses the Banshee (B+NN), Raven (R+NN), and Queen of the Night (Q+NN) in his 10x11 variant "Twenty-first Century Chess" (1991). The (B+NN) and (R+NN) pieces are called the Unicorn and the Varan in Glenn Overby II's 11x11 variant Abecedarian Big Chess (2002). Note that the first two variants mentioned are played on boards that are taller than they are wide.

Computer Play: Fergus Duniho was kind enough to playtest this game with me in 2001 and create a PBM preset here. I started work on a Zillons Rules File for this game, but ended up making one for Lions and Unicorns Chess (on 80 squares).