Oh, well, here's the item I designed...
This chessboard of natural ebony and white pine is often found open in a wizard’s study, with matching pieces in initial position for a game. The board’s owner may fold it in into a 4-inch by 4-inch by 1-inch thick object. The pieces disappear when folded and reappear when opened. Their location depends upon the board's position when previously folded. If a game was in progress, the chessmen appear in the prior game’s configuration. If not, they appear in their initial positions.
Upon viewing the open board, any (non-owner) character must make a Will Save DC 19 or be geased to play. When playing alone against the board, it is considered to have an Int of 21 and 10 ranks in Profession: Chess Player.
To own it, one must first defeat it. If the board wins, the character must make a Will of 16 plus the difference between the character’s & the board’s check. Failure means the player is geased to play another game immediately as if by a twelfth-level caster.
Owning the chessboard confers the following benefits: +4 bonus to Concentration and Knowledge (Tactics).
Strong Enchantment, CL 12, Craft Wondrous Items, Geas/Quest, Price 3,200 gp.