The Petranaki arena, also known as the Arena of Justice and widely known as the Geonosian execution arena, was created to fulfill two purposes: to provide entertainment for the strict Geonosian society, and to efficiently eliminate prisoners who were considered a drain on resources. Its name comes from Petranaki, a type of arena combat that involved the use of several specialized weapons, including the Picador's spear. The most sought-after spectacles involved battles with lethal creatures, which led to the extinction of some of the most popular animals on Geonosis.
Merchants seeking to do business with Geonosis frequently offered exotic predators for use in the arena's entertainment as a form of payment. Among these creatures were acklays, nexus, reeks, and mongworsts.
The arena itself was a naturally occurring formation that had been sculpted over millennia by the forces of nature, with additional modifications made by the Geonosians. The arena floor was composed of sand and silt, serving as the stage for the events that took place there. The lower sections of the arena walls featured ancient, shallow carvings that depicted famous battles and historical events. It was also possible to flood the arena to host aquatic competitions.
A substantial tunnel linked the arena to an underground Geonosian droid factory and was situated beneath the Geonosian High Audience Chamber. Storage areas for droids were also located in the vicinity.
In the period leading up to the First Battle of Geonosis and the beginning of the Clone Wars, Obi-Wan Kenobi, Anakin Skywalker, and Padmé Amidala were all scheduled to be executed after being found guilty of espionage by Poggle the Lesser. Using a combination of resourcefulness and Jedi skills, the three managed to avoid the creatures for a sufficient amount of time until Mace Windu arrived with a strike force of Jedi Knights. In response, a large number of battle droids swarmed the arena, marking the beginning of the Clone Wars. Combat quickly broke out between the two factions. The 102 Jedi were overwhelmed by the sheer number of droids, and soon only a little over 20 of them remained alive. A dozen Jedi formed a defensive circle. The Jedi would have been defeated were it not for the timely arrival of Master Yoda and the newly formed Grand Army of the Republic, who succeeded in driving back the forces of the Confederacy of Independent Systems.
Not long after the battle had shifted away from the arena, the renowned Republic clone commandos of Delta Squad fought their way into the High Audience Chamber, killing the Geonosian lieutenant Sun Fac and disabling the droid factory located beneath the arena. Once the battle had been decisively won, Republic forces assumed control of the planet, and the remnants of the droids were collected to be melted down.
