There are 7 kinds of pieces in the starting array:
- Pawn - These behave just like Shatranj pawns (i.e. like modern chess pawns without an initial double-step option or en passant).
- Knight - The same as modern chess knights (leaping in an L-shape over any intervening pieces). The knight promotes to a warrior.
- Fers (councillor) - Steps one square at a time diagonally. In Shatranj, this is the equivalent of the modern queen, but here it replaces the alfil (elephant), which is the equivalent of the modern bishop. The fers promotes to a bishop.
- Thief - Leaps two squares diagonally or orthogonally over any intervening pieces. Fairy chess problemists call this piece an "alibaba" (alfil + dabbabah), so I called it a thief. It is colorbound, and can only visit ¼ of the squares on the board. If necessary, it may be represented on the board by a single checker (black for black, red for white). It promotes to an assassin.
- Wazir (vizier) - Steps one square at a time orthogonally. Represented in a modern set by the queen. It promotes to a grand vizier.
- Rook - The same as the modern rook: sliding any number of squares orthogonally until reaching an obstacle or the edge of the board. It is the one starting piece that does not promote.
- King - Same as the modern chess king. Moves one square at a time orthogonally or diagonally. It may not move into a threatened square nor remain under attack at the end of the player's turn (check), and the game is lost when it cannot avoid capture (checkmate). It promotes to a warrior king.
The following pieces are obtained only through promotion. To mark them, I suggest placing a checker under the basic piece (so a warrior would be a knight on top of a checker, an assassin would be a stack of two checkers, etc.).
- Warrior - This piece may move as a knight, or may move one space orthogonally.
- Bishop - The same as a modern bishop: sliding any number of squares diagonally until reaching an obstacle or the edge of the board.
- Assassin -The thief does not gain a new form of movement by promotion. Instead, it gains a new form of capture, by overtaking: the assassin may capture by jumping over an enemy piece and landing on an unoccupied square. While it is still can only visit ¼ of the squares on the board, it is capable of capturing pieces on all squares with the exception of the player's first rank and the file opposite where the thief started. Note that the assassin may only capture by overtaking if its landing square is empty; it cannot capture two pieces (one by overtaking, one by displacement) in a single move.
- Grand Vizier - Moves as a king (one square, any direction), but is not subject to restrictions against moving into or staying in threatened squares, and it may be captured like any other piece. It may additionally promote to a regent by returning to the player's first rank.
- Warrior King - May move as a king or as a knight. Rules regarding check and checkmate are still in force.
- Regent - Moves as a king or grand vizier. When a player has a regent, he is immune to check and checkmate, and his king (or warrior king) may freely move into or stay in threatened squares. If the king is captured, the regent immediately becomes the new king (thus there is no more regent, and check and checkmate are once again enforced). Note that if a warrior king is captured, the regent still only becomes a plain king, not a warrior king; however, it may promote as a king.
Checkmate is a win. Stalemate is a win. Baring the king (capturing all of an opponent's pieces except for the king) is a win, unless the opponent can bare one's own king in the next move, which is a draw. There is no castling and no en passant. These rules are all the same as in shatranj.
The occasional rule that a king in check may switch places with a friendly piece once in a game is not present (the wazir/grand vizier/regent promotion track serves a similar purpose). The medieval chess rule of the "king's leap" (the ability for a king to make a knight's move once per game) is also not present (the promotion of the king to warrior king gives a more general mechanism for this).
The idea is to get a more dynamic game using primarily short-range pieces (like classic shatranj). The two sides start very close to each other, letting the weaker pieces get into the thick of things more quickly. All of the pieces' movements are either found in shatranj or shatranj variants (like Tamerlane Chess), or are combinations of those moves. For example, the thief combines the 2-square diagonal leap of the traditional shatranj alfil (a very weak piece, only capable of reaching 1/8 of the squares on the board!) with the 2-square orthogonal leap of the dabbabah (war machine), which is found in some old variants. The only exception is the assassin's capture, which has no equivalent in any predecessor or traditional relative of chess (with the possible exception of the chu shogi lion, which is considerably more powerful). The double promotion of the wazir and "substitute king" rule is adapted from the "pawn of pawns" and "pawn of kings" rules of Tamerlane Chess.
The assassin's capture can be quite dangerous: an assassin may capture a piece that is "protected" by another piece without risk of being captured.
I haven't decided how pawns should promote. One option is to let them promote to any other starting piece (other than the king, of course), which can not promote further. Another is to stick with the shatranj promotion rule in this case and only allow them to promote to the queen-equivalent (in this case, the wazir) without being able to promote further. Still another would be to allow promotion to any basic type, with the ability to promote further by reaching the player's 1st rank. I'm undecided.
Another change I'm pondering is adding two more thieves to the initial array (bringing it up to 4 thieves per player), starting on the 1st rank, each a knight's move away from the closest thief on the 2nd rank. This would allow all of a player's thieves, taken together, to visit any square on the board. Since these 1st-rank thieves could never reach the 8th rank, they would have to promote on the 7th. I'm currently leaning towards this.