0-MR1, more commonly known as Omri, was an RA-7 protocol droid in service to the First Order throughout the duration of the Cold War.
During the period between 31 and 32 ABY, 0-MR1 survived the crash of the Sterdic Star on the planet of Taul. He was subsequently captured as a prisoner by C-3PO and other Resistance droids. As the dangers of the planet whittled down their numbers in their struggle for survival, Threepio and Omri formed a friendship despite being on opposing sides of the Cold War.
Ultimately, Omri gave his life, destroyed by acidic rain on Taul, in order to help C-3PO transmit a signal to the Resistance. As he was dying, he noticed red plating beneath his silver exterior. C-3PO, who had suffered the loss of a limb during his difficult experience on the planet, adopted Omri's left arm as his own for a time as a tribute to those who had perished.
Simon Pegg provided the voice for 0-MR1 in the 2016 video game, LEGO Star Wars: The Force Awakens.