(25.02.2014) A fairy original by Geoff Foster - a rare example of KoBul Kings in Duplex form (and probably the first one of this type with 2x2 solutions).

White:

1…Kb4 2.nSf5 nQxf5(bK=rS)+ 3.rSd2 Kc3#

1…nSg8 2.Kd5 nQxg8(bK=rS)+ rSc7 Kb6#

Black:

1…nSf5 2.nQb7+ Kxf5(wK=rS) 3.rSxb7(bK=rQ) rQd5#

1…nQg8 2.nSxg8(bK=rQ) nSe7 3.nSd5 rQxd5(wK=rS)#

Echo mates (Author)

KoBul Kings: when a piece (not a pawn) of his own side is captured, a King transforms into a Royal piece of the same type as the captured one. When the King is in the form of any Royal piece and there is a capture of one of the pawns of his own side, he becomes a normal King again.

Neutral piece: a unit with this characteristic may be regarded as of either colour by the side whose turn it is to play. Neutral pawns promote to neutral pieces.