2 You have a king and an antiking. King cannot be let in check, but antiking
3 must always stay under check. Antiking captures his own kind.
6 A new piece is introduced: the antiking, noted by the letter 'A' in diagrams
7 and PGNs. This piece must always remain under (orthodox) check: it is
8 considered in (anti-)check when not attacked by any enemy piece. In such a
9 situation, the antiking must move immediately to an attacked square.
12 The antiking is a royal figure, and thus cannot be captured.
13 It captures only the pieces of his color (to help checkmating the opponent's
14 antiking, but this also complicates standard checkmate).
16 figure.diagram-container
18 | fen:rnbqkbnr/pppppppp/3A4/8/8/3a4/PPPPPPPP/RNBQKBNR c5,d5,e5:
19 figcaption Marked squares are not allowed antiking moves.
23 Although antiking captures his color, it doesn't check his king - it
24 doesn't check the opponent's king either.
26 Since it would allow a basic tactic (keep antiking touching opponent's
27 king), kings do not attack antikings.
31 p There are two ways to win:
33 li Checkmate opponent king
34 li Anti-checkmate opponent antiking
36 ...Or do both at the same time, as on the following diagram after 3.Qxf7#
37 (the black antiking was on g3).
39 figure.diagram-container
41 | fen:rnbqkbnr/pppp1Qpp/1A6/4p3/4P2a/8/PPPP1PPP/RNB1KBNR h4,e8:
42 figcaption After 1.e4 e5 2.Qh5 Ah4?? 3.Qxf7#
47 a(href="https://www.chessvariants.com/diffobjective.dir/anti-king-chess.html")
49 | on chessvariants.com.