The challenge was made from one member to another by unsheathing a coutari - the traditional Centauri blade used by the Couro Prido - and driving it into a solid object between the duelists. The challenged duelist accepted the challenge by taking the coutari from its place and bringing it to the duel.
In a duel, the two combatants met each other in their ordinary clothes - sans jacket - only adding a quilted, decorated vest and gloves to provide protection from glancing blows and slashes. The two met face-to-face on a round section of carpet that served as the dueling ring; both combatants had to stay within that area. This allowed by-standers to stand nearby and watch the duel commence.
The combatants unsheathed their coutari, faced each other, saluted with their swords, and bowed. After that, the duel commenced and only ended when one of the combatants were dead. They could go directly for killing blows or else wear down the opponent by a number of shallow strikes intended to bleed and wound. The laws of the Couro Prido were established to maintain the strength of the Centauri noble houses. Upon striking the killing blow, the victor accepted the loser's family into his house.
In 2259, Urza Jaddo - an elected member of the Centauri Populum - learned that a resolution had been placed before the Centaurum, declaring him a traitor. He went to his fellow member of the Couro Prido, Londo Mollari, for help. Londo went to Lord Antono Refa to try and get the resolution dropped before voting on it, but Urza became livid, as it was Refa who brought the resolution. As a result, Urza took one of the coutari he intended to give Londo as a gift of their alliance and used it to challenge him to the Morago.
The two met in battle, Urza taunting Londo with the fact that he could never best him with a coutari. Londo retorted that his life had never been at stake before. Both men bled each other with repeated strikes, until Urza drove Londo to the ground. As Urza lifted his blade to strike the killing blow, Londo regained himself and stabbed up, straight through Urza's torso.
Urza complemented Londo on a blow well-struck, and then he died in Londo's arms. Londo knew that Urza was indeed superior with a coutari and had thrown the duel, that he allowed Londo to kill him. After this, Londo vowed to get to the bottom of what was happening in the Centaurum back on Centauri Prime and personally blamed Lord Refa for the death of his friend. By the laws of the Couro Prido, Urza's family became part of House Mollari upon Urza's death. As such, they were spared from the consequences of the Centaurum's resolution, which had been Urza's plan all along.
From that day onward until he left Babylon 5, Mollari kept the pair of coutari he and Urza used in the duel on the wall of his quarters.