Tai shogi

Tai shogi is a large-board variant of Japanese chess that emerged during the fifteenth century, combining nearly all of the pieces found in two other oversized shogi variants, dai dai shogi and maka dai dai shogi, while adding nine pieces unique to itself. It is played on an enormous 25 by 25 grid of 625 squares, with each player commanding 177 pieces drawn from 93 distinct piece types, and unlike ordinary shogi it does not allow captured pieces to be dropped back onto the board, instead promoting pieces only when they make a capture. Victory requires capturing both the opposing emperor and prince pieces, but a single game can require well over a thousand moves per side and stretch across multiple sittings, which meant tai shogi never became a widely played pastime; historical records point to only one production run of six complete sets in the early seventeenth century, suggesting it survived mainly as a prestige display set rather than a game people regularly sat down to finish. Before the 1997 rediscovery of taikyoku shogi, tai shogi was believed to be the largest playable board game ever devised.