Re-Ghost Chess

Suddenly imagined FIDE-based variant…

Idea of ghost pieces was created in 2021 with my α-ChBrTi but then denied.

Re- means revenging/returning/renewing & links to my nickname Rechefiltr_is_Fire.

Rules

Setup and pieces are as in Chess.

If piece is captured, it’s placed in its owner’s (which remains unchanged) hand, but as very modified form called ghost (among other traits, this form doesn't block long trajectories, both friendly and foe, incl. another ghosts' motions). Hand is capable only for one ghost: if new piece is captured, hand is refreshed and previous placeholder is eliminated from a game. Five moves (10 half-moves) after the last piece is captured, player can drop its ghost on the board instead of moving (freely, except for Pawn which cannot be dropped on the farthest four ranks), but only one ghost per player can be there. Ghost can be taken like normal piece, and in this case it's eliminated from a game; new ghost can be dropped only five moves (10 half-moves) after previous one of its owner is taken. Compare below:

Moving to square occupied by friendly piece is illegal. 
Pawns' ghosts can promote only to other pieces' ghosts.
Object of the game is to checkmate opponent’s King.

Draw occurs if:

• One player is stalemated (he/she can’t do any legal move and hasn’t any ghost; otherwise, if there's no legal moves but ghost exists, it can be dropped even after less than five moves, so game continues).
• 50 moves (100 half-moves) are done without capture / promotion / ghost drop.
• There's threefold repetition of position (incl. same types of pieces' ghosts in hands).
• There're 2 Kings without other pieces & ghosts in any hand.
• One player hasn’t any pieces & ghosts, and another has 1 or 2 Knights or 1 Bishop, no matter normal or ghosted (aka insufficient material).

Last revised by Lev Grigoriev.