(22.06.2013) A non standart fairy problem with Sentinelles and Magic Square by Luis Miguel Martin from Spain.

a) Black King on c2
1.Kb2(+bPc2) 2.Ka1(+bPb2) 3.b1R 4.c1Q=w Qa3#
b) Magic square on c2
1.Kb2 2.Ka3(+bPb2) 3.b1Q 4.Qc2=w Qb3(+wPc2)#

Like a twin exchanging c1 and c2 squares
[its content (bK) and its properties (magic)].
Author

Sentinelles: When a piece (Pawn excluded) leaves a square outside the first and last rows, it leaves a Pawn of the color of the side that played unless 8 Pawns in this color are already on the board.
Magic Square: A piece whose move ends on this square changes color.