This chess variant, where one piece generates another, appeared much earlier than my E-Chess, where the same idea of generating was used, but in a different cyclicality. Complications arising in 'BOTK' forced me to put this chess variant aside for a while and concentrate on the lighter version of E-Chess.
Now, when I had the opportunity to test 'BOTK', I was able to delve deeper into my creation and get answers to my questions.
I dare say that 'BOTK' is the most complex of all chess variants using a regular 8x8 board and the same pieces as in classical chess.
Setup. Standard chess setup, except that there are no chess pieces on the first and last rank. The rest of the pieces appear on the board during the game.
The movement of pieces and their 'reproduction'. Chess pieces move across the board as they do in ordinary chess - according to the standard rules of move and capture. After a piece leaves the square on which it stood, a new chess piece appears on this square, according to the following chain of cycles: Pawn - Knight - Bishop - Rook - Queen - King.
Thus, after the pawn's move, a knight appears on the square where this pawn stood. On the square where the knight stood, after its movement, the bishop appears, and so on until the king appears. So one piece generates another, and only the king does not generate any pieces during its movement. With each move, the fields of the board fill up, turning a chess battle into an unprecedented opposition of chess pieces.
The appearance of the King on the square where it is threatened with check is unacceptable. This means that if your Queen is under attack, then you will not be able to deflect it from the blow, since the King will appear in the place where the Queen is. A player wins the game when he/she checkmates his/her opponent's king (s). To win, it is enough to checkmate one King. A check to kings is considered checkmate if at least one of them is unable to escape from this check. A stalemate is a win for the player delivering the stalemate. The player made a move leading to a repetition of the position (which is only possible if there are kings on the board) losses. There is NO DRAW in this chess variant.
More details here >>> https://www.chess.com/blog/Pokshtya/battle-of-the-kings-is-a-chess-variant-that-drives-you-crazy
and here >>> https://www.chessvariants.com/rules/battle-of-kings-
Here is an example of the first moves of the game:
1. e3 e6
2. Ng3 d6
There is no irony in the name of this chess variant, because the Kings are you and only you decide when, how and where to appear on the battlefield.