RB-551 was an outdated B1-series battle droid model. He fought as part of the droid army belonging to the Confederacy of Independent Systems during the Clone Wars. During 21 BBY, the battle droid participated in the Confederacy's attempts to seize control of the planet of Ryloth. He was a member of a battle droid patrol tasked with finding the Twi'lek Resistance that was fighting the droid army to free the planet. Unfortunately, RB-551 and the rest of his patrol were destroyed by the Twi'lek freedom fighters. This led the Confederacy to send more battle droids to find out what happened to the missing patrol.
RB-551, an older B1-series battle droid model, was under the command of a Central Control Computer. He fought as part of the droid army of the Confederacy of Independent Systems during the Clone Wars against the Galactic Republic. The planet Ryloth was invaded by the Separatist Droid Army, including RB-551, in 22 BBY under the command of Techno Union Foreman Wat Tambor during the war.
Later, in 21 BBY, the droid army faced resistance from the Twi'lek Resistance, which was headed by General Cham Syndulla and was trying to free their [homeworld](/article/homeworld] from Separatist rule. The Confederacy sent RB-551 and a patrol of other battle droids to the cratered flatlands of Cazne to find and destroy the Twi'lek resistance fighters. However, the resistance fighters ambushed and destroyed RB-551 and his patrol as they moved through the area. Because of this, the Confederacy deployed more battle droids to find the missing patrol. After discovering his remains, the other droids discussed how RB-551's reliance on a central computer contributed to his demise.
RB-551's remains first showed up in "Liberty on Ryloth," the twenty-first episode of the first season of the Star Wars: The Clone Wars TV show, which was broadcast on March 13, 2009. Matthew Wood, who also voiced all other B1-series battle droids in the series, provided RB-551's voice in the episode.