Although Plo Koon only had a few fleeting appearances in the Star Wars films, his backstory is rich. A Jedi Master of the Kel Dor species, Plo was among one of the wisest members of the Council. He served during the final years of the Galactic Republic, aiding in the Clone Wars, before eventually being killed in Order 66. Plo was also the Jedi who found Ahsoka Tano and took her to the Jedi Temple. However, Ahsoka went on to become Anakin's Padawan, not Plo's. However, he did train a few of his own apprentices. Here, we'll go into who these Jedi were, and what became of them.
Bultar Swan
Bultar Swan was a Jedi of the Human species. Most of the information known about her is provided in the non-canon Star Wars Legends; however, she did make a brief appearance in Attack of the Clones during the Battle of Geonosis. Bultar was born on the planet of Kuat during the final decades of the Galactic Republic, but the Jedi took her from her homeworld and brought her to the Temple at an early age to begin training. She was first assigned to tutelage under Jedi Master Micah Giiett, where she learned and excelled at martial arts. Bultar then trained under Master Plo Koon, who taught her the art of lightsaber defense.
Bultar was strongly dedicated to her beliefs in the Jedi ways and the Light Side of the Force. She was commended among the Jedi for having never killed an opponent prior to the Clone Wars. During the Clone Wars, Bultar served the Republic alongside her peers as a Jedi General, leading armies into battle on multiple planets. She even helped defend the Republic's capital, Coruscant, in a defining battle against the Confederate Navy.
When Emperor Palpatine initiated Order 66, Bultar did evade the initial Great Jedi Purge. While on the run, she was contacted by another survivor, Shadday Potkin, who invited her to meet on Kessel along with eight other Jedi. But Shadday had an ulterior motive — instead of offering simple asylum, she had called her peers to Kessel in hopes of rallying them to join forces against Darth Vader, who was on his way. Indeed, Vader arrived and slew most of these Jedi, but Bultar and Master Tsui Choi disarmed him. True to her peacekeeping nature, Bultar refused to kill the defenseless Sith Apprentice. But her fellow Jedi, Koffi Arana, was intent on doing so. Koffi seized her lightsaber to attack Vader, but in doing so, he stabbed Bultar and ended her life.
Lissarkh
According to Legends, Lissarkh was a Force-sensitive female of the Trandoshan species. As a youngling, she was brought from her home planet Trandosha to the Jedi Temple to receive training. Plo Koon claimed her as his Padawan, and he taught her the ways of the Light Side of the Force for many years. Eventually, Lissarkh was promoted to the rank of Jedi Knight right before the Invasion of Naboo in 32 BBY.
During the Clone Wars, Lissarkh served as General of the Republic's Grand Army until the fateful Order 66. She was taken in the Great Jedi Purge when her own Clone troopers turned on her without hesitation.
Unidentified Padawan
Jedi Master Plo Koon's final apprentice of the Legends canon remains largely unidentified, and not much is known about the Padawan. They were a Force-sensitive being who, several months into the Clone Wars, appeared before the Jedi Council and was then sent to the planet Dorin. There, Plo Koon agreed to train them as his Padawan.