Same as 20, except it automatically loads from a specific library position. The usual set of pieces is arranged randomly on the first and eighth ranks, with bishops on opposite colors, and the king between the two rooks, and Black's arrangement a mirror of White's. Double-check only counts as one. You must capture if possible. The king plays no special role and can be captured or left en prise.
Pawns can promote to king.
Win by losing all your pieces or getting stalemated. See also wild 17, Losers Chess. The ancient precursor to chess.