Regicide is a human tabletop game played across the Imperium of Man. It uses a board and pieces or can be played using a virtual holographic display. It is similar to the ancient Terran game of chess, and can be played on a "hooded" board where only certain pieces are visible, making the game more complex. It is known that this game was played by Chief Librarian Petrok of the Iron Snakes Space Marines Chapter as a trainee Librarian to improve his tactical ability without relying on his psychic talents.
Ciaphas Cain was a competent player, often playing against officers of the Imperial Guard during downtime, including the Lord-General Zyvan.