An Icehouse game by Nate Straight.
The ancient Indian game, Chaturanga, believed to be a predecessor of Chess enters the Icehouse world. In this four-player variant, two partnerships compete against each other.
The object is to capture, rather than simply checkmate, your opponents' two monarchs.
4 stashes of Icehouse pieces (black, red, green, and yellow is traditional; but, in these rules, blue is substituted for black, so that the most common Icehouse colors are all used)
2 four-sided dice per player, matching each player's color of Icehouse pieces
1 chessboard large enough to comfortably fit a large Icehouse piece
4 players, in 2 partnerships of 2, and approximately 30 minutes
knowledge of standard Chess rules is both necessary and assumed
knowledge of standard Martian Chaturanga rules is very helpful
Each player will form a monarch, a paladin, a raven, three squires, and a throne from their stash of Icehouse pieces, as described below.
A monarch consists of a full tree of Icehouse pieces: a small on top of a medium on top of a large. A paladin consists of a broken tree of Icehouse pieces: a small on top of a large. A raven consists of an unfinished tree of Icehouse pieces: a medium on top of a large. A squire consists of the top of a tree of Icehouse pieces: a small on top of a medium. A throne consists of the remaining two larges stacked on top of each other. The board is placed between the four players such that each player has one side of the board facing them. The blue and green players are one partnership and must sit across the board from each other; the red and yellow players are the other partnership and must also sit across the board from each other. Pieces are placed on each player's right-hand corner. The board is setup as if each player had only one half of the standard Martian Chaturanga setup (which is, for all practical purposes, a scaled-down version of the standard Chess setup), located in their right-hand corner. For setup (and movement), it is also helpful to think of the raven as being equivalent to a rook, the paladin as being equivalent to the merger of a knight and a bishop, the monarch as being equivalent to the merger of a king and a queen, and the squires as being equivalent to the pawns in a standard Chess setup.
On each player's home row (the row nearest them), they will place their raven on their right-hand corner (just like one of the rooks in Chess), their paladin on the square horizontally adjacent to the raven, and their monarch on the square horizontally adjacent to the paladin; they will place their three squires directly in front of their raven, their paladin, and their monarch. The throne is placed off the board immediately below the monarch (the throne serves only as a marker, and never moves). See the pictures below:
Each of the four types of pieces (excluding the throne, which never moves) is assigned a specific number to be used in determining piece movement during the game. The number assignments conveniently correspond to the alphabetical relationships of the first letters of the four pieces' names, with the name with a first letter nearest to A being assigned a value of 1, and so on.
Monarch = 1, Paladin = 2, Raven = 3, and Squire = 4.
Each player rolls one dice, and the partnership with the highest total will start. That partnership chooses one of their two players to begin. Play passes clockwise after that.
On each player's turn, they will roll both of their four-sided dice and then move the two pieces indicated by the roll, as determined by the number assignments above. A player may freely choose to move either, both, or none of the pieces indicated by their roll, in any order. If either piece indicated by the roll is unavailable (due to capture by the opponent), the player may count upwards from the number rolled until reaching a number assigned to a piece that is available. The count ends at 4 and may not wrap around to 1.
The four types of pieces move according to rules of movement implied by each of their names and the standard rules of movement in Chess. A monarch is a combination of a king and a queen, and may move as either (in effect, as a queen). A paladin is a type of "holy knight," such as might be found if a knight and a bishop merged, and may move as either a knight or a bishop. A raven is sort of an upgrade from a rook (both are birds from similar families), and may move as a rook, but may also move two (and only two) spaces in any direction diagonally, "flying" over any piece found in between. A squire is simply a renamed pawn, and moves exactly as such. Pieces capture and are captured exactly as they are in Chess, with the exception of the omission of the "en pasant" capture.
There is one special move, called the "unkindness of ravens" ("unkindness" is the term for a group of ravens, like "murder" is the term for a group of crows; this move is exactly like the "triumph of boats" in traditional Chaturaji), which may be performed if the dice, piece positions, and previous piece movements allow it. The unkindness of ravens may occur only when three players' ravens occupy three of the central four squares on the board and the fourth player, whose raven does not occupy one of those squares, rolls and moves their raven into the unoccupied central square. When this move occurs, the fourth player simultaneously captures all three of the other ravens (even their own partner's raven) from the board, leaving only their own raven left on the square that it moved to.
Finally, as in Chess, if a player's squire manages to reach the opposite home row (their partner's home row) it may be promoted to any other piece that that player has had captured by their opponent. [this rule may later be amended to fit with traditional rules]
If a player's monarch is captured by either of their opponents, that player is not immediately out of the game. There are a few recourses, as described below.
If a player's monarch has been captured, their remaining pieces are left where they stand and may continue to be captured. That player is not immediately out of the game, but they may not roll the dice or move any of their pieces when it comes to their turn; they must pass to their opponent. However, any other player whose monarch still remains in the game may move their monarch to the space marked by the throne of the player whose monarch has been captured, and thus take control over that player's pieces so long as they maintain control of the throne space. Therefore, on any player's turn at the beginning of which their monarch is located on the throne space of another player whose monarch has been captured, that player may roll both their dice and the dice of the player whose monarch has been captured (even if the player whose monarch has been captured is one of their opponents), thus controlling two sets of pieces on that turn (a player is not required to have their monarch located on their own throne in order to move their own pieces, obviously). Also, if a player's monarch has been captured and their partner's monarch is located on the throne of the player whose monarch has been captured at the beginning of the captured player's turn, the player whose monarch has been captured may roll their dice and move their pieces instead of passing their turn to their opponent.
If a partnership has had one of their monarchs captured by their opponent, and then captures one of their opponents monarchs, they may choose to allow both of the captured monarchs to be returned to play. This is not necessary and is not always the best strategic choice, but it is possible, and allows a partner who has been defeated to reenter the game. When a partnership chooses to allow both of the captured monarchs to be returned to play, the players whose monarchs they are will place the monarchs onto the board in any vacant square on their own home row (or, failing that, any vacant square on their second row). The partnership that made the capture of the second monarch may choose whether they will place their monarch first or allow their opponents to place their monarch first.
The game ends when a partnership successfully captures both of their opponents' monarchs, regardless of whether both of their own monarchs remain on the board after the capture of their opponents' monarchs. There are no checks or checkmates in the game; the partnership that actually captures the opponents' monarchs wins.
In general, it is probably better to move to your partner's throne rather than to capture an opponent's monarch and allow both monarchs to be returned, since it is quite possible that the monarch which you capture may be returned to the board in such a way as to immediately defeat one of your own monarchs on that player's next turn, which may very well be the next turn in line. Consider the ramifications of the reentry rule before using it.