The Rules, In Brief
King — one step, any direction.
Queen — leaps exactly two squares in any of the eight directions, clearing any piece in between.
Rook — slides orthogonally, any distance.
Bishop — slides diagonally, any distance.
Knight — the ordinary knight's leap.
Pawn — one step in its own forward direction, capturing one step diagonally forward. Air & Fire pawns advance up/down the board; Water & Earth pawns advance across it. No castling, no double step.
A throne square (the four corners) starts held by a king and a partner piece together. If an enemy captures a still-doubly-held throne, both pieces fall at once.
A king in check must move if it has any legal step at all, even into another check — only if it is boxed in by its own side may another piece be played instead.
When a king is captured, its whole army is frozen: the pieces stay on the board as obstacles, but can never move, threaten, or be captured again.
A pawn promotes to the piece it served (queen, rook, bishop, or knight) on reaching the far edge — but only once that piece has already been lost.
Allies never threaten or capture one another. The game is won when both kings of an alliance have fallen.
Not implemented here: seizing a friendly throne, exchanging captured kings, the privileged-pawn exception, the bishop/queen concourse captures, and stalemate/bare-king draws — all genuine but rare Golden Dawn refinements.