The shadow rules · v3
Cast — instead of moving, place a piece's shadow on a square it could
reach along an open line — no jumping over pieces, so clear a path (move your pawns!). A
shadow may land on an enemy piece that blocks it — a marked attack; next
turn's swap captures it. Never on your own piece. N/B/R/Q may cast; pawns never; the King only
once your queen has fallen or a pawn has promoted.
Up to 3 shadows — keep as many as three out at once. Cast a 4th and your
oldest shadow fades (first in, first out). Each piece may hold
only one shadow — casting again from it moves its shadow.
Swap — the owner may teleport to its shadow at any later turn. If an enemy piece is standing
on the shadow square, the swap captures it. Blocked only by your own piece.
Unkillable, unknowing — shadows can't be captured or blocked; enemies may land on the square
and stand there — at their peril.
The anchor holds — a shadow stays where cast even as its owner roams the board.
It fades only when its swap is used, its owner dies, or it's the oldest of four.
Shadows never block, never capture by themselves, never give check. No casting while in check.