Fairy chess piece
A fairy chess piece, variant chess piece, unorthodox chess piece, or heterodox chess piece is a chess piece not used in conventional chess but incorporated into certain chess variants and some unorthodox chess problems, known as fairy chess. Compared to conventional pieces, fairy pieces vary mostly in the way they move, but they may also follow special rules for capturing, promotions, etc. Because of the distributed and uncoordinated nature of unorthodox chess development, the same piece can have different names, and different pieces can have the same name in various contexts.
Most are symbolised as inverted or rotated icons of the standard pieces in diagrams, and the meanings of these "wildcards" must be defined in each context separately. Pieces invented for use in chess variants rather than problems sometimes instead have special icons designed for them, but with some exceptions, many of these are not used beyond the individual games for which they were invented.
Background
The earliest known forms of chess date from the 7th century in Persia and India. They had different rules from the modern game. The game was passed to the Arabs, then to the Europeans, and for several centuries, it was played with those ancient rules. For example, the queen was once able to move only a single square diagonally, while the bishop could jump two squares diagonally. The change of rules occurred in Spain in the end of the 15th century when the queen and the bishop were given their modern moves. In the old Muslim manuscripts those two pieces were referred as ferz and fil. The queen is still called ferz and the bishop is called slon in Russian and Ukrainian. The bishop is still called alfil in Spanish. Due to the pieces' change in movement, the ferz and the alfil are considered non-standard chess pieces. As those who created modern chess did in the 15th century, chess enthusiasts may still create their own rule variations and how the pieces move. Pieces that move differently from standard rules are called "variant" or "fairy" chess pieces.The names of fairy pieces are not standardised, and most do not have standard symbols associated with them. Most are represented in diagrams by rotated versions of the icons for normal pieces, though a few exceptions sometimes get their own icons: the equihopper and the knighted pieces, and a few of the basic leapers. The common names for the pieces are used here whenever possible, but these names sometimes differ between circles associated with chess problems and circles associated with chess variants.
Classification
Many of the simplest fairy chess pieces do not appear in the orthodox game, but they usually fall into one of three classes. There are also compound pieces that combine the movement powers of two or more different pieces.Simple pieces
Leapers
A leaper is a piece that moves directly to a square a fixed distance away. A leaper captures by occupying the square on which an enemy piece sits. The leaper's move cannot be blocked – it "leaps" over any intervening pieces – so the check of a leaper cannot be parried by interposing. Leapers are not able to create pins, but are effective forking pieces. A leaper's move that is not orthogonal nor diagonal is said to be hippogonal.Moves by a leaper may be described using the distance to their landing square – the number of squares orthogonally in one direction and the number of squares orthogonally at right angles. For instance, the orthodox knight is described as a -leaper or a -leaper. The table to the right shows common names for the leapers reaching up to 4 squares, together with the letter used to represent them in Betza notation, a common notation for describing fairy pieces.
Although moves to adjacent squares are not strictly "leaps" by the normal use of the word, they are included for generality. Leapers that move only to adjacent squares are sometimes called step movers in the context of shogi variants.
In shatranj, a Persian forerunner to chess, the predecessors of the bishop and queen were leapers: the alfil is a -leaper, and the ferz a -leaper. The wazir is a -leaper. The dabbaba is a -leaper. The 'level-3' leapers are the threeleaper, camel, zebra, and tripper. The , giraffe, stag, antelope, and commuter are level-4 leapers. Many of these basic leapers appear in Tamerlane chess.
Riders
A rider, or ranging piece, is a piece that moves an unlimited distance in one direction, provided there are no pieces in the way. Each basic rider corresponds to a basic leaper, and can be thought of as repeating that leaper's move in one direction until an obstacle is reached. If the obstacle is a friendly piece, it blocks further movement; if the obstacle is an enemy piece, it may be captured, but it cannot be jumped over.There are three riders in : the rook is a -rider; the bishop is a -rider; and the queen combines both patterns. Sliders are a special case of riders that can only move between geometrically contiguous cells. All of the riders in orthodox chess are examples of sliders.
Riders can create both pins and skewers. One popular fairy chess rider is the nightrider, which can make an unlimited number of knight moves in any direction. The names of riders are often obtained by taking the name of its base leaper and adding the suffix "rider". For example, the is a -rider. A nightrider can be blocked only on a square one of its component knight moves falls on: if a nightrider starts on a1, it can be blocked on b3 or c2, but not on a2, b2, or b1. It can only travel from a1 to c5 if the intervening square b3 is unoccupied.
Some generalised riders do not follow a straight path. The aanca from the historical game of Grant Acedrex is such a "bent rider": it takes its first step like a ferz and continues outward from that destination like a rook. The unicorn, from the same game, takes its first step like a knight and continues outward from that destination like a bishop. The rose, which is used in chess on a really big board, traces out a path of knight moves on an approximate regular octagon: from e1, it can go to g2, h4, g6, e7, c6, b4, c2, and back to e1. The crooked bishop or boyscout follows a zigzag: starting from f1, its path could take it to e2, f3, e4, f5, e6, f7, and e8.
A limited ranging piece moves like a rider, but only up to a specific number of steps. An example is the short rook from Chess with different armies: it moves like a rook, but only up to a distance of 4 squares. From a1, it can travel in one move to b1, c1, d1, or e1, but not f1. A rider's corresponding leaper can be thought of as a limited ranging piece with a range of 1: a wazir is a rook restricted to moving only one square at a time. The violent ox and flying dragon from dai shogi are a range-2 rook and a range-2 bishop respectively.
There are other possible generalisations as well; the picket from Tamerlane chess moves like a bishop, but at least two squares These are in general called ski-pieces: the picket is a ski-bishop. A skip-rider skips over the first and then every odd cell in its path: it cannot be blocked on the squares it skips. Thus a skip-rook would be a, and a skip-bishop would be an. A slip-rider is similar, but skips over the second and then every even cell in its path.
In some shogi variants, there are also area moves. These are similar to limited ranging pieces in that the pieces with such moves repeat one kind of basic step up to a fixed number of times, and must stop when they capture. However, unlike other riders, they may change direction during their move, and do not have a fixed path shape like riders or bent riders do.
Hoppers
A hopper is a piece that moves by jumping over another piece. The hurdle can be any piece of any color. Unless it can jump over a piece, a hopper cannot move. Note that hoppers generally capture by taking the piece on the destination square, not by taking the hurdle. The exceptions are locusts which are pieces that capture by hopping over its victim. They are sometimes considered a type of hopper.There are no hoppers in Western chess. In xiangqi, the cannon captures as a hopper along rook lines ; in janggi, the cannon is a hopper along rook lines when moving or capturing, except it cannot jump another cannon, whether friendly or enemy. The grasshopper moves along the same lines as a queen, hopping over another piece and landing on the square immediately beyond it. Yang Qi includes the diagonal counterpart of the cannon, the vao, which moves as a bishop and captures as a hopper along bishop lines.
Compound pieces
Compound pieces combine the powers of two or more pieces. The queen may be considered the compound of a rook and a bishop. The king of standard chess combines the ferz and wazir, ignoring restrictions on check and checkmate and ignoring castling. The alibaba combines the dabbaba and alfil, while the squirrel can move to any square 2 units away. The phoenix combines the wazir and alfil, while the kirin combines the ferz and dabbaba: both appear in chu shogi, an old Japanese chess variant that is still sometimes played today.An amphibian is a combined leaper with a larger range than any of its components, such as the frog, a --leaper. Although the -leaper is confined to one half of the board, and the -leaper to one ninth, their combination can reach any square on the board.
When one of the combined pieces is a knight, the compound may be called a knighted piece. The archbishop, chancellor, and amazon are three popular compound pieces, combining the powers of non-royal orthodox chess pieces. They are the knighted bishop, knighted rook, and knighted queen respectively. When one of the combined pieces is a king, the compound may be called a crowned piece. The crowned knight combines the knight with the king's moves. The dragon king of shogi is a crowned rook, while the dragon horse is a crowned bishop. The knighted compounds show that a compound piece may not fall into any of the three basic categories from above: a princess slides for its bishop moves, but leaps for its knight moves. Combinations of known pieces with the falcon from falcon chess are named winged pieces, in Complete Permutation Chess not only winged knight, bishop, rook, and queen are featured, but also winged marshal, winged cardinal, and winged amazon.
Marine pieces are compound pieces consisting of a rider or leaper and a locust in the same directions. Marine pieces have names alluding to the sea and its myths, e.g., nereide, triton, mermaid, and poseidon. Examples named for non-mythical sea creatures include the seahorse, dolphin, anemone, and prawn. Games that consist of these marine pieces, known as "sea chesses", are often played on larger boards to account for these pieces needing more squares available for their locust-like capturing moves.