In politics, when a king is weak or losing power, often a lonely soldier will rise through the ranks, organize the troops, and replace him. Sovereign Chess models this possibility by allowing a pawn to promote to a king, with the result that the original king is removed from the board. As we will see, this can happen in two distinct ways, with differing results.
Figure 13: Now You Have Him...
In Figure 13, Black is in trouble. White controls the Slate pieces, and by sliding out the bishop, has just exposed the Black king to check by the Slate queen. Trapped behind some well-placed pawns, the king is trapped, but Black is not lost. In Figure 14, the Black pawn on i11 dutifully promotes and takes his rightful place as king, immediately exiling the old king from the board in the process, and saving checkmate.
Figure 14: ...Now You Don't!
Not only did this move save the game for Black, but it effectively allowed the king to "jump" to the center of the board, where it may find safe haven from the White pieces by moving to h9. However, if a piece controlled by the White player had been threatening i10, the promotion would have been illegal, and Black would have lost.
Figure 15: Black King in Trouble...
Any move in Sovereign Chess which affects the leadership of the army is called a regime change, and such a promotion--when a pawn becomes a king of the same color--constitutes a coup d'état.
An overthrow occurs when a player promotes a pawn, of a different color than his king, to a king of that color. Figure 15 again has Black in trouble, and White has just gained control of the Yellow pieces. While not in check, the Black king is vulnerable, and with few Black pieces left, hard to defend.
Yet, Black controls the Violet pieces, specifically the pawn on k8. By moving the pawn to j8, and promoting it to a Violet King, there are many ramifications. First, as we will see in Rule #11, the player now becomes Violet, and can move the Violet pieces without occupying either Violet square. Also, the player loses control of the remaining Black pieces, unless control can be regained by occupying one of the Black squares in the center of the board.
Figure 16: ...Is Overthrown by the Violet King!
What is the advantage to the player in overthrowing his own king? Like the first example, he makes a speedy retreat to mildly safer territory. But more importantly, he gains exclusive use of a Violet queen, rook, bishop, knight, and remaining pawns--less than the Black army he started with, but more than the Black survivors.
And what about all those pieces of different colors we keep talking about? Let's go to Rule #11...