Iridonia was the homeworld of the Zabrak species. Due to the harsh living conditions, the Zabrak were a hardy species. They took to flight and then space travel as soon as they could develop the technology, and by the time the Duros encountered them, they had already colonized five systems. Notable Iridonians included Darth Maul, Agen Kolar, Bao-Dur, Drell Kahmf, Sirak and Maris Brood.
As a Mid Rim world situated near important hyperspace lanes, Iridonia was one of the key worlds that connected the Outer Rim to the Inner Rim. As such, it was often one of the first planets to be pulled into a war. During the Old Sith Wars, the planet was the site of numerous battles.
A battle at Iridonia, fought during the Great Sith War, was a major victory for the Galactic Republic. It was a turning point in the war which gave the Republic Military and the Jedi Order momentum which would help them to eventually defeat their Sith adversaries.
Several of Iridonia's colonies along the Outer Rim were conquered by the Mandalorians during the initial stages of the Mandalorian Wars. After learning of the loss of their colonies, many Iridonians, including Bao-Dur, sought revenge by joining the Republic's war effort against the Mandalorian invaders. In the same year, 3963 BBY, the Mandalorian Neo-Crusaders launched a major offensive against Iridonia. After a successful campaign, they occupied the planet for a number of months, but Iridonia was eventually liberated by the Republic Military.
Iridonia changed hands a number of times during the Jedi Civil War. The Sith Empire and the Republic fought fiercely over the planet, and both sides used it as a staging ground during the conflict. Due to the fact that Iridonia was occupied by the Sith at times, the eight Iridonian colonies became self sufficient. Following the war, they broke away and became independent worlds.
Around 1002 BBY, the Brotherhood of Darkness operated a Sith academy on the world that trained Sith Acolytes and apprentices. The Sith also hired Zabrak mercenaries from the planet's high council.
After the Ruusan campaign, the Zabrak established colonies on many far-flung worlds. The Zabrak of Iridonia maintained the most militant culture, and Zabrak youths from the colonies were often sent to the original homeworld for warrior training.
Kaysil Verwood became the first New Republic Senator of her people, representing not only Iridonia but all the Zabrak colonies. The Zabrak were founding members of the government, as Verwood attended the Galactic Caucus to form the new government.
At some point after the formation of the New Republic, Luke Skywalker visited the world as an ambassador to help with opening new trade routes to the Outer Rim Territories. While staying on the planet, he encountered a solid-state hologram said to be the ghost of the Dathomirian Zabrak Sith Lord, Darth Maul. The ghostly image had terrified the Zabrak government for some time, driving one council representative to the brink of madness. Skywalker tracked the apparition down to a laboratory run by the Zabrak scientist Drell Kahmf who claimed to have salvaged the brain of Maul and constructed the hologram body for it to reign havoc on society. The Jedi was appalled at the torment of the disembodied man and disconnected the device keeping the brain alive.
When Darth Krayt's Galactic Empire was first established, Iridonia was amongst the first world to pledge its allegiance to the new Emperor. Since Zabraks were traditionally a species that produced many Force-sensitives, Iridonia contributed more apprentices to the One Sith than any other world. However, despite the wishes of Iridonian government, several Zabrak colonies rebelled against the new Empire. Two such colonies were completely wiped out when Pellaeon-class Star Destroyers issued Base Delta Zero to reduce their planets to rubble. After the punishment the remaining five colonies surrendered to Imperial forces and one of them, Feldrona, was transformed into a prison planet and placed under tight Imperial control.