Salt (Sa) moves one square diagonally on its own board to a vacant square of the same colour — or straight up/down one board, into the same square.
Mercury (M) moves anywhere on its own board, or to any square two boards up or down — colour doesn't matter.
Sulfur (S) moves to any vacant or enemy square on any of the seven boards.
Every piece has two components, e.g. Sa:M. The first component sets how it moves. After each move a piece advances through the cycle: Sa:Sa → Sa:M → Sa:S → M:Sa → M:M → M:S → S:Sa → S:M → S:S → back to Sa:Sa.
Landing on an enemy piece captures it. Capture every one of your opponent's 27 pieces to win.