FirstGen Zero-Three was one of the early members of the race of sentient mechanical beings known as the Sentries. At some point he was exiled by the other FirstGen Sentries because his views were considered too radical for him to remain. At some point during this long exile Zero-Three attempted to enter the Null's home in subspace and destroy it, but Zero-Three was unable to enter the subspace realm. Afterward it would conclude that the fight against the Null was hopeless.