Lore was a Soong-type android constructed by Dr. Noonien Soong and Juliana Soong at the Omicron Theta colony and activated on September 9, 2335. Built in Dr. Soong's own image, Lore was the fourth android they constructed and the first successful example of a fully-functional positronic brain. An earlier model Soong-type android, B-4, also had a positronic brain but of a less sophisticated type. Lore was extremely advanced and sentient, possessing superior strength, speed and intelligence when compared to a Human. Lore's emotional programming was very advanced; but he began displaying signs of emotional instability and malevolence.

Eventually Soong capitulated, but not before Lore had secretly contacted the Crystalline Entity, offering it the planet's life to ensure his own survival. After deactivating and dismantling Lore, Soong set about constructing his brother Data, an android without destabilizing emotions. Soong placed Lore's components into storage, intending to eventually correct his behavioral problems. Lore later harbored resentment towards his creator for abandoning him. Yet, when he met his father again on Terlina III and learned that Soong was dying, he was sincerely upset and for a brief moment he displayed a genuine concern for his father. Nevertheless, his malevolent streak soon prevailed.

Following Lore's communiques, the Crystalline Entity attacked Omicron Theta in 2336 and destroyed all life on the planet. Both Lore and Data were left behind, but Data was discovered in 2338 by the crew of the USS Tripoli. Lore remained in Soong's lab until 2364, when the USS Enterprise-D arrived at the planet. The ship's chief engineer, Lieutenant Commander Argyle, and chief medical officer, Dr. Beverly Crusher, were successful in reactivating the android. Lore immediately returned to his previous ways, deactivating his brother, stealing his uniform, and masquerading as him. He summoned the Crystalline Entity once again, intending to feed the crew of the Enterprise to it. His treachery was discovered due to the differences between him and Data (such as his use of contractions in speech), and he was transported into open space.

(TNG: "Datalore", "Silicon Avatar")

Lore drifted in space for nearly two years until he was rescued by a passing Pakled ship. Lore subsequently answered the homing signal intended to draw Data to Soong's new laboratory on Terlina III. Soong had intended to give Data an emotion chip that would allow him to feel Human emotions. However, once again Lore tricked Soong and posed as his brother, stealing the chip for himself, and then in a burst of anger he fatally injured his father. Lore escaped before he could be apprehended.

(TNG: "Brothers")

Lore's positronic net was unique from Data's in that it had a Type-"L" phase discriminator, compared to Data's Type-"R".

(TNG: "Time's Arrow")

In 2369, Lore discovered a group of Borg that had been disconnected from the Collective after receiving Hugh's sense of individuality. Lore made himself their leader, gave his Borg individual names, turned them into his fanatical followers and began cruel experiments on them, trying to replace their organic brains with positronic components.

Meanwhile, he somehow influenced their behavior, making their attacks more violent - they ceased to assimilate people, instead murdering them. He directed his Borg to launch attacks on Federation space to lure the Enterprise and thus Data, in an elaborate attempt to use the emotion chip to manipulate Data to his side. Lore modified the chip so that it could remotely instill anger and hatred in Data. Confused with his new emotions, and with his ethical program deactivated, Data betrayed the crew of the Enterprise and joined Lore at his base.

(TNG: "Descent")

While in Borg captivity, Geordi La Forge was able to instruct Captain Jean-Luc Picard in modifying a Borg interlink transceiver to reset Data's ethical program with a kedion pulse, restoring his sense of right and wrong; he would still experience negative emotions, however, he could at least choose whether or not to act upon them. Upon realizing Lore's malign nature, Data fired upon and deactivated Lore, whose last words were "I... love you... brother." Lore was subsequently dismantled and the emotion chip, though damaged, was removed and returned to its rightful owner.

(TNG: "Descent, Part II")