Sisseri Deo was a Jedi apprentice at the Jedi Temple during the time of the Clone Wars. A Firrerreo, he was two and one third meters tall with an above average muscular build and a golden skin tone. At the height of the Clone Wars, Sisseri participated in the Jedi Apprentice Tournament on Coruscant. Sisseri was the one apprentice that many of the students had picked to win the entire competition.

He sped through the first round with ease and took out Forzi Ghul in the second round with a swift roundhouse kick. The third round set the final eight contestants against each other in a dining room brawl and free-for-all. As evening meal began, Jedi Master Ilena Xan began discussing the tournament and the fact that fights can happen anywhere. Sisseri Deo and the rest of the competitors immediately knew that a fight was about to ensue and began to strategize the attack. Sissero Deo picked out Tallisibeth Enwandung-Esterhazy, the one contestant most students picked to lose.

As Ilena Xan was making her speech, Tallisibeth secretly positioned herself behind Seisseri to wait until the battle began. When Ilena Xan gave the signal, Tallisibeth sprang into action throwing juice into Sisseri's face, giving her a momentary advantage. While he was distracted, Tallisibeth grabbed onto Sisseri's tunic and used it to choke him. Despite his physical advantage, Sisseri was unable to shake Tallisibeth off his back and slowly succumbed to lack of oxygen. Just before he passed out, he yielded making Tallisibeth the tournament champion.