The ship was built in the Allanteen Six shipyards, and incorporated modifications provided by Jedi Knight Anakin Skywalker. Its first engagement was to defend the Kothlis spynet against General Grievous. The crew dealt with the Confederacy of Independent Systems' new jamming techniques, related to sabotage during construction. Lieutenant Avrey, the communications officer, jury-rigged a solution using decades-old technology. The ship's complement of Clone troopers routed the enemy, but in the process, took heavy casualties and gained serious damage to the port side of the vessel. The damage limited hyperdrive effectiveness and would place the ship in space-dock for weeks. Senator Bail Organa, head of the Senate Security Committee would start a task force to ascertain the cause of the sabotage after the battle.
A few weeks later, word of the mission to Lanteeb undertaken by the Jedi Obi-Wan Kenobi and Anakin Skywalker reached the Jedi Temple and Senator Organa. In order to rescue the two Jedi and stop General Lok Durd, who was developing a bioweapon, repairs to the Indomitable were fast-tracked. Jedi Master Yoda sent the Indomitable to Lanteeb with a flotilla consisting of Pioneer and Coruscant Sky. Admiral Yularen was joined by Torrent Company and Skywalker's Padawan, Ahsoka Tano. Master Mace Windu took the Dagger from its patrol in the Bothawui system and joined the Indomitable at the pre-approach coordinates.
Upon reversion to realspace, the fleet discovered the Separatists had blockaded the planet, and General Grievous himself was present. Windu ordered Lt. Arey to raise the Jedi Temple on a priority channel. The countermeasures put in place prevented the Separatists from jamming communications again, blocking four attempts during Windu's conversation with Yoda. Yularen and Windu disagreed on the next course of action, but agreed to wait one hour before provoking Grievous.
In order to rescue Skywalker and Kenobi, Senator Organa had lent a captured Separatist spy ship to Master Taria Damsin. She planned on using the ship to infiltrate the blockade by faking pursuit by the Republic forces and a subsequent crash-landing. To fool the Separatist fleet into thinking the ship was theirs, the Republic flotilla launched squadrons of V-19 Torrent starfighters to harass the opposing ships. Master Damsin arrived in the middle and gave out a falsified distress call while she was chased by Gold Squadron from the Indomitable, as well as Arrow Squadron and Hammer Squadron. She successfully crash-landed on the planet and assisted Skywalker and Kenobi while the orbital battle continued.
After fourteen hours of back-and-forth clashes, Admiral Yularen was ready to cut his losses and fall back. Yoda contacted Windu and informed him Senator Organa and Senator Padmé Amidala had scraped together a fleet from government and corporate entities to liberate Lanteeb. When the fleet arrived, it numbered eleven starfighter squadrons and various other ships. Grievous lost his nerve and fled the system, allowing the Indomitable to launch its complement of Low Altitude Assault Transport/infantry gunships and take Torrent Company to rescue Skywalker, Kenobi, and Damsin.
With the battle over, the fleet rested twelve hours over the planet while the aftermath was sorted out. The Jedi left on a shuttle to Dagger, which would return them to Coruscant.
The Indomitable appears in 2010's Clone Wars Gambit duology. The ship is described as a Jedi cruiser, a nickname for Venator-class Star Destroyers during the Clone Wars.