FirstGen One-Five was a member of one of the early series of the race of sentient mechanical beings known as the Sentries.
In 2381, members of the USS Titan's crew and other Sentries met aboard One-Five. At this meeting he would construct a new frame to carry SecondGen White-Blue's core. Later, he was present at the meeting in dataspace where SecondGen Red-Gold launched his rebellion the FirstGens. When a Null incursion occurred following the attempted coup, One-Five commanded the Sentry forces against the Null, which was eventually stopped by the Titan. After the battle it would ask Captain Will Riker of Titan what the Sentries could do now that their prime directive had been accomplished, to which Riker said they could do anything. (TTN novel: Synthesis)