SecondGen White-Blue was a second generation Sentry.
In 2381, White-Blue went to investigate a Null incursion outside of its home system. This investigation led to the destruction of White-Blue's shipframe and its discovery by the USS Titan. This discovery led to White-Blue's nexus core, essentially its brain, being taken aboard the Titan where it made contact with the ship's crew. Shortly after White-Blue made contact, SecondGen Cyan-Gray entered the area in order to salvage White-Blue's shipframe and attacked Titan, taking it for a threat. In order to stop the attack White-Blue was forced to enter Titan's computer system and send a message to Cyan-Gray, while in the computer he sensed an intelligence there and offered it the chance to become sentient, an opportunity which it would accept.
In order to repair the damage that had been done, Titan was towed into the Sentry's home system where the ship's crew and White-Blue went before the Governance Kernel. It was here that White-Blue was given a new platform to carry its nexus core and made the supervisor of the Sentry's repairs to Titan. In this capacity he was overseen by members of Titan's crew to ensure that he didn't enter the computer and tamper again.
After Titan helped engage the Null, the Sentries held a meeting in dataspace which White-Blue took Christine Vale into. At this meeting SecondGen Red-Gold revealed his plan to take the Titan and use it to fight the Null, which White-Blue immediately informed Titan of. During this battle the final Null incursion began and Titan's Avatar had to close the subspace rift through which the Null was entering normal space. This action freed all the Sentries from their core directive, essentially giving them freedom to chose their own futures, which White-Blue used to board Titan and ask Captain Riker if he could stay aboard. (TTN novel: Synthesis)
In 2382, White-Blue was part of an away team to the terraforming device known as Brahma-Shiva. Following the disabling of a memory pack, White-Blue offered to allow the AI of the device to transfer into his memory core so that it could survive the destruction of the Brahma-Shiva by antimatter bombs. The AI of Brahma-Shiva (considered to be a reincarnation of the Great Egg Bringer S'Yahazah of Gorn mythology) disabled White-Blue during the attempted transfer. When reactivated by Torvig Bu-Kar-Nguv aboard Titan, White-Blue informed his friend that their nightmare had only begun. (TTN novel: Seize the Fire)
White-Blue then went quiet again, and Torvig tirelessly worked to restore him or at least the information he had gained from the Brahma-Shiva AI on terraforming. When Titan arrived at the Vela Pulsar, an AI from the planet Ta'ith in that system transferred itself aboard Titan and entered into a three-way mind link with White-Blue and Tuvok. Both Tuvok and White-Blue willingly agreed to the link to help the Ta'ithan AI Maintenance Module One One Six save its planet from destruction. On the away mission to the planet's surface, One One Six was restored to its computer, but had sustained too much damage to survive. White-Blue and Tuvok melded with it again in order to keep it together long enough to save the planet. At the end of that meld, White-Blue decided to remain merged with One One Six in the planet's computer core, abandoning his body to help permanently protect the Ta'ithan people from the Vela Pulsar's deadly radiation. Meanwhile, his body was taken back to Titan, and Torvig began working once again to restore White-Blue's intelligence from his archived files. (TTN novel: Fallen Gods)