Twin-board Ecumenical Chess

There are twice as many non-Pawns as in FIDE Chess, and in the simplest forms this was reflected in using 2 ranks of a board with 8 files by either 8 or 10 ranks, depending on whether there is a Pawn rank or not. Both preserve the FIDE pattern of four ranks between the camps. An alternative is to use two complete FIDE boards, with Pawn and non-Pawn ranks on both, joined either side by side as in Ralph Betza's Doublewide Chess or back to back as in Köksal Karakus' Besiege Chess. Either might be done twice over to create a wraparound, as in Köksal Karakus' Torus Chess.

Setup

.

WRAPAROUND ECUMENICAL CHESS
This variant distributes compound pieces in four pairs throughout the first rank as all files are, in a sense, middle files. Note that Rooks are put far apart, as would not be the case were the Rook files from Northern EC simply joined together.

.

BESIEGE ECUMENICAL CHESS
In SINGLE BESIEGE EC the board is as shown and each player has disadvantages - White's divided army and Black being attacked on two fronts, as in Besiege Chess.

In DOUBLE BESIEGE EC the board is wrapped round at the end ranks, so that both armies are united and both attacked on two fronts, as in Torus Chess.

.

MOEBIUS ECUMENICAL CHESS
As Double Besiege EC, but the ends are wrapped round the wrong way round. This means that each file joins up not to its own other end but to that of the "opposite" file. This unbinds Bishops, Camels, and Caliphs as well as allowing Rook and Bishop moves twice as long as in Double Besiege EC.

.

I have also created an Ecumenical form of Quadruple Besiege Chess.

Pieces

	The fourth elemental piece is a 3:1 leaper called the CAMEL, whose Square Of Leap Length (SOLL) is twice the Knight's. There are two Camels aside, the same number as other elementals. In the special case of Quadruple Besiege EC, the 3:1 leap is effectively the same as the 7:5, 9:5, 11:7, 13:1, and 15:3, leaps.
	The extra compounds of FIDE pieces are variously named but MARSHAL and CARDINAL are popular names among game inventors, now including myself. There is one of each per side, the same number as Queens.
	Another compound with an existing name is the GNU (Knight+Camel), also known by other names including the exact synonym Wildebeest. There is one Gnu per side, the same number as Queens.
	The other two compounds are not historic ones. The CANVASSER (Rook+Camel) is a pun suggestion someone packing tents on a camel, but really means someone carrying out surveys from house to house - though not necessarily houses as grand as that represented by the Rook! The CALIPH (Bishop+Camel) is a title of leaders in early Islam, and that religion spread widely on lands with camels. Each army has one Canvasser but two Caliphs, the latter piece being colourbound in most variants. This makes the Caliph remarkably weak for a compound - but conversely remarkably strong for a colourbound piece!

Rules

In all forms of Besiege EC except Quadruple, which has no Castling, Castling is as FIDE Chess but Kingside only. In Northern EC, the King moves four cells towards either Rook and the Rook moves to the last cell that the King passes through. In Wraparound EC the King can castle with a wider choice of pieces, which must have a Rook move:
King to file k via Kingside, Canvasser to file j;
King to file f via Queenside, c-file Rook to file g;
King to file m via Kingside, Marshal to file l;
King to file d via Queenside, Marshal to file e;
King to file n via Kingside, c-file Rook to file m;
King to file c via Queenside, Canvasser to file d;
King to file b via Queenside, k-file Rook to file c;
King to file a via Kingside, Queen to file p.
In each case no cell on the route taken by the King may be threatened by an enemy piece. Note that there are four castlings each way, and no to are to, the same destination.

Checkmate and Stalemate are as in FIDE Chess.

Notes

Pieces can be represented by two distinguishable FIDE sets. Unlike other forms of Ecumenical Chess, these subvariants require both lots of Pawns to represent Pawns themselves (or one lot Pawns and one lot Yeomen). The rule of large K/Q and small B/N/R as themselves, small K/Q as Cardinal/Marshal, and large R/B for Canvasser/Caliph may be retained, but the Gnu should be represented by an unturned large Rook to free the large Knights for representing Camels.