Community variant
Praetorian chess
Praetorian Chess is a βdifferent armiesβ variant in which classical White (RNBQKBNR) faces the Praetorian army VWXIKXWV (this setup has an empirical White score of 50.365%).
The rules are otherwise those of standard chess, except that there is no castling. Check, checkmate, en passant, and ordinary pawn movement are unchanged. Pawns promote to Queen, Rook, Bishop, or Knight.
Praetorian pieces:
- V Arbalest (Roobis, mRcB): moves like a Rook, but captures like a Bishop.
- W Sentinel (Rooman, mRcK): moves like a Rook, but captures one square in any direction.
- X Praetorian (Bers, KR): combines Rook and King movement.
- I Ballista (Bisroo, mBcR): moves like a Bishop, but captures like a Rook.
- K Caesar: the ordinary royal King.
Empirical piece values computed in this matchup:
Praetorian X (Bers) = 5.98
Ballista I (Bisroo) = 3.87
Arbalest V (Roobis) = 3.64
Sentinel W (Rooman) = 3.28
Queen Q = 8.50
Rook R = 4.26
Bishop B = 3.28
Knight N = 2.97
Pawn P = 1.00
This is a user-catalogued casual variant. Technical details such as board size, FEN, pieces, and hand rules are defined in the Fairy-Stockfish variants.ini block below.
Generated rule overview
This variant inherits its base rules from `chess` and overrides the settings shown below.
Board and setup
Pieces and movement
- The piece set used on the board is: king (k), queen (q), rook (r), bishop (b), knight (n), pawn (p), custom piece 15 (w), custom piece 14 (v), bers (x) and custom piece 8 (i).
- custom piece 8 (i) is a custom piece with Betza movement `mBcR`.
- custom piece 14 (v) is a custom piece with Betza movement `mRcB`.
- custom piece 15 (w) is a custom piece with Betza movement `mRcK`.
Move rules
- Castling is not allowed.
Promotion
- The pieces that can promote are: pawn (p).
- Promotion choices are both sides: queen (q), rook (r), bishop (b) and knight (n).
Piece movement
These diagrams show custom pieces and known Fairy-Stockfish built-in fairy pieces from White's perspective on a compact preview board. Some special moves, especially hoppers and game-state-dependent moves, can still depend on blockers or game state.
mBcR
mRcB
mRcK
move
capture
move or capture
initial only
hopper target
Fairy-Stockfish rules
[praetorian:chess]
# Classical pieces
knight = n
bishop = b
rook = r
king = k
# Move/capture hybrids
customPiece8 = i:mBcR
customPiece14 = v:mRcB
customPiece15 = w:mRcK
# Built-in compound pieces
queen = q
bers = x
# Pawn and promotion rules
pawnTypes = p
promotionPieceTypes = qrbn
# The experiment has no castling
castling = false
# Classical White vs vdrnkrdv Black
startFen = vwxikxwv/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1