The Brek'tal ritual was a Klingon rite that allowed the widow who was the head of their House to marry the opponent who had slain their husband. This was allowed in conditions where the deceased left no heir to become the leader of the House. However, unique circumstances can allow the widow to be granted special authority to continue leading the House on her own. (DS9 episode: "The House of Quark", ST references: Klingon for the Galactic Traveler, Celebrations)