Alekhine Chess
Alekhine chess was invented by Michael Wortley Nolan (known as MrWCF on cowplay) and is the first variant on cowplay to include non-standard chess pieces. The game of Alekhine Chess is played on a 14x8 board and includes 3 new piece types, the Cardinal, the Marshall and the General as shown in Figure 1.
Alekhine Chess Setup
Figure 1
Rules
All standard chess rules apply to this variant, including en-passant, pawn's 2-square advance, castling and promotion.
Cardinal, Marshall and General
The new piece types available in Alekhine chess are combinations of standard pieces as follows:

Cardinal = Knight + Bishop
Marshall = Knight + Rook
General = Knight + Queen
PGN Extension
The PGN notation for the new pieces is simply 'C' for Cardinal, 'M' for Marshall and 'G' for General used similarly to standard piece names.
Castling Variation
To begin with, the Marshall, which can be seen to inherit a rooks movement (as might the General), cannot castle with the king. Castling is restricted to 'real' rooks only in Alekhine chess.

Castling both to the left and to the right in Alekhine chess with the rooks on the 'a' and 'n' files involves moving the king one square from the edge of the board. For example, the white king castling to the left involves the king being moved to 'b1' with the rook formally on a1 being moved to 'c1'. Alternatively, the white king castling to the right involves the king being moved to 'm1' with the rook formally on 'n1' being moved to 'l1'. All standard castling rules involving the king being in check apply to this variant also.