c. 32 BBY
Shadow Twelve and his fellow pilots from Shadow Squadron were assigned a mission from General Skywalker where they had to go through a nebula to reach the Kaliida Shoals medical center and destroy a giant warship made by the Separatists to save the center. Shadow Twelve, the clone pilots of Shadow Squadron, and Jedi Anakin Skywalker, Ahsoka Tano, and Plo Koon, left the Venator-class star destroyer Resolute, Skywalker's flagship, and departed for the nebula. After some discussion, they reached the nebula and went inside. Soon, it was discovered that the Balmorra Run, the route they were taking, was infested with giant neebray mantas. Shadow Squadron all evaded the creatures and took no damage, except for a scratch on Matchstick's ship.
After coming out of the nebula, the Malevolence came out of hyperspace in front of them and started their attack on the med center. The Malevolence launched a detachment of their vulture droids to destroy them, but when that didn't kill them, the giant ship launched a giant ion blast, attempting to disable them. Shadow Twelve and his squadron directed their ships above, and Shadow Seven, Ten, and Six were disabled in the blast. Two more were killed by fighters, leaving about half of their squadron left.
Being low on numbers, the small group of fighters flew towards the Malevolence and tried to disable it. Once figuring out how to defeat it, Anakin directed his troops to fire proton torpedoes at the main ion cannon, attempting to disable it. They shot, and when the Malevolence fired, it overloaded and blew up. The squadron then left the ship after crippling it.
Shadow Twelve had Phase I clone pilot armor with grey markings on it. He had two dark grey Republic symbols on either side of his helmet, and he had a life-support pack on his chest. His dark grey markings were the colors of his unit, Shadow Squadron.