Inside the Fort, there is an arena at which men (and only men) can boast of their battle prowess in a gladiatorial setting. Speak to Otho about fighting in the arena. During combat, only a machete and gladiator armor can be used; all other equipment is removed from the player's inventory. There are three rounds, and after each one Otho must be spoken to again to begin the next.
After each fight, your items are returned to your inventory all at once, but each one has its own on-screen pop-up message. These messages can take several minutes to clear. To avoid this, the player can place items in any nearby footlocker before starting the quest and collect them at the end. Even though the footlockers are marked as owned, retrieving your items from them does not count as stealing. Saving the game after a fight and then reloading will also cancel the pop-ups.
After killing Stella and finishing this quest, most of the Legion soldiers around the camp will start commenting about you saying that "they had never seen someone killing an NCR Ranger in the first round in the arena".
Behind the scenes
Laurifer gladiator loosely translates from Latin as "victorious gladiator".
PCXbox 360 After fighting against the two slaves, you can put your holdout weapons into their inventory. If you immediately start another round in the arena (against Sergeant Andrews) before the slave's bodies disappear, you can get your weapons from the slave's inventory and fight him with your holdout weapons. This can also be done to fight against Ranger Stella.
↑Fallout: New Vegas Official Game Guide Collector's Edition p.370: "Free Quest: Laurifer Gladiator Otho runs the arena, and he's always looking for challengers to his stable if indentured gladiators. This is a purely small-time operation, but you can ask to compete in the arena, as well as learning the rules (only a Machete, Melee Weapon combat, and light armor). To the death! You can also ask him about how the arena fights work, the Legate, and the Burned Man. For every battle you win, you receive Fame, and the chance to fight a more seasoned opponent." (Fallout: New Vegas Official Game Guide Collector's Edition Tour of the Mojave Wasteland)