p.boxed.
	You have a king and an antiking. King cannot be let in check, but antiking
	must always stay under check. Antiking captures his own kind.

p.
	A new piece is introduced: the antiking, noted by the letter 'A' in diagrams
	and PGNs. This piece must always remain under (orthodox) check: it is
	considered in (anti-)check when not attacked by any enemy piece. In such a
	situation, the antiking must move immediately to an attacked square.

p.
	The antiking is a royal figure, and thus cannot be captured.
	It captures only the pieces of his color (to help checkmating the opponent's
	antiking, but this also complicates standard checkmate).

figure.diagram-container
	.diagram
		| fen:rnbqkbnr/pppppppp/3A4/8/8/3a4/PPPPPPPP/RNBQKBNR c5,d5,e5:
	figcaption Marked squares are not allowed antiking moves.

ul
	li.
		Although antiking captures his color, it doesn't check his king - it
		doesn't check the opponent's king either.
	li.
		Since it would allow a basic tactic (keep antiking touching opponent's
		king), kings do not attack antikings.

h3 End of the game

p There are two ways to win:
ol
	li Checkmate opponent king
	li Anti-checkmate opponent antiking
p.
	...Or do both at the same time, as on the following diagram after 3.Qxf7#
	(the black antiking was on g3).

figure.diagram-container
	.diagram
		| fen:rnbqkbnr/pppp1Qpp/1A6/4p3/4P2a/8/PPPP1PPP/RNB1KBNR h4,e8:
	figcaption After 1.e4 e5 2.Qh5 Ah4?? 3.Qxf7#

h3 More information

p
	a(href="https://www.chessvariants.com/diffobjective.dir/anti-king-chess.html")
		| Antiking chess
	|  on chessvariants.com.