If you are like most people, you have never heard of Hnefatafl (or just Tafl for short). This board game is a much lesser-known cousin of chess. One army sits in the middle of the board with their king, who seeks to reach one of the corner squares. The opposing army has no king and sits in four groups on the edges of the board and seek to either block off the corners or surround the king on four sides. All pieces move like a rook in chess.
For a more in depth set of rules, check out this website: http://aagenielsen.dk/tafl_rules.php
Enjoy!