Proxy

PROXY was the only known witness to his master being knighted by Darth Vader. Shortly afterwards, he traveled with Galen when he was sent to eliminate Rahm Kota.

After many missions, including rounding up the Rebel leaders, PROXY eventually accompanied Galen and Juno Eclipse to the signing of the Corellian Treaty. Darth Vader and Imperial troops ambushed Senators Iblis, Organa, and Mon Mothma. PROXY in a bold move managed to save the lives of Galen and Juno by using his hologram capabilities to disguise himself as Obi-Wan Kenobi. Darth Vader was momentarily fooled, enough for Marek and Eclipse to get away. Vader, being immensely superior to PROXY in lightsaber combat destroyed the droid and succeeded in capturing the Senators

Some time after his master’s demise at the hands of Emperor Palpatine, he was recovered from the snow and harsh winds on Corellia by Bail Organa and Juno. They were recovering records of the birth of the Alliance and wanted PROXY because he had the records of the origin, Marek. PROXY continued to retell them exactly what had happened to lead Galen down the path of redemption.

Source: Wookiepedia