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4 Player chess

First of all... I want a set like that (assuming that your board is cross-shaped)!
These are the rules I would use:
REGARDING THE KING: If a king is in check, he has to avoid the check the same way one does in normal chess. If the king moves to avert the check, he cannot move into the line of fire of a piece belonging to the attacker or a third side.
In 4-player chess, capturing kings are possible. Once a king is captured, the capturing piece becomes the new king of the former king's remaining army (in my case, I indicated the new king by placing a checker piece under the capturing piece).
In 4-player chess, it is also possible to pass a turn. Because of this, there is no such thing as stalemate.
to be continued...

MOVE ORDER AND NAMING:
Instead of by colour, the players are refered to by "Northern Kingdom", "Western Kingdom", etc. Or, if you want to be creative, create exotic new names for the kingdoms, or have your opponents do it themselves, for their kingdom. In this case, I will simply refer the four kingdoms as "north", "south", "east", and "west".
North moves first, then east, then south, then west.
Once a kingdom takes over another kingdom, the conquering kingdom becomes an "empire", and the conquered kingdom becomes a "province" of the empire.
If a province is captured, the province is lost. If an empire is captured, reign over both it and its province will be given to the new conquerer. Therefore, at the end of the game, an empire will have three provinces.
to be continued...

OPTIONAL FUN RULES:
NOTE: OPTIONAL RULES ARE OPTIONAL
At any time, a player may offer to sign a "pact" with another player. If he/she agrees, the two kingdoms become temporary allies. The pact automatically expires when, through the harmonious teamwork of the two allied kingdoms, the remaining two kingdoms are conquered and only they remain. If the one who offered the pact captures a piece belonging to the one he/she offered the pact too, the pact is broken, and the two allies are enemies again. To compensate for the captured piece, a piece of the same material value belonging to the violator of the pact is chosen by the one who stayed loyal to the pact and taken off the board. If the violator of the pact does not have adequate pieces for compensation, all of his/her pieces are taken off the board, leaving only a bare king. Alternatively, the violator loses his/her entire kingdom, and thus, the game.
I bought a chessboard that is large and which is made for 4 player chess. Each player begins on each side (north,west,south,east.) The thing is how do you play it?? If one player is in check, what happens? Is it even possible to play it? If it is..please tell me how (: