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'.
  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.
  Antikings don't give check, and kings do not attack antikings.

figure.diagram-container
  .diagram
    | fen:2prbkqA/2p1nnbr/2pppppp/8/8/PPPPPP2/RBNN1P2/aQKBRP2:
  figcaption Initial setup: antikings stand in the corners.

h3 Unusual moves

ul
  li.
    Pawns are Berolina Pawns, which move diagonally forward one square
    without capturing, or move one square straight forward to capture.
  li.
    If a King or Anti-King has not yet moved, it may make as its first
    move a Knight's leap to an empty square.

h3 End of the game

p There are three ways to win:
ol
  li Checkmate opponent king
  li Anti-checkmate opponent antiking
  li Give a double check, as on the following diagram

figure.diagram-container
  .diagram
    | fen:2pr3A/2pb1qbr/2p1pkQp/2pnp1n1/1PPN4/PPB1PPN1/1K2RP2/a2BRP2:
  figcaption After Qb1xg6#

h3 More information

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

p Inventor: Peter Aronson (2002)