(covers information from several alternate timelines)
Boratus was a male Vorgon criminal from the 27th century who, along with his partner, Ajur, attempted to steal a device known as the "Tox Uthat", a quantum phase inhibitor capable of halting all nuclear fusion within a star.
In order to prevent the Uthat from falling into the wrong hands, Kal Dano, the Uthat's inventor, traveled back in time to the 22nd century and hid it on Risa. Having failed to obtain the Uthat, Boratus and Ajur searched historical records and discovered that Jean-Luc Picard would discover and destroy it in 2366. Traveling back to that point in time, they told Picard that they were security agents and that they wished to retrieve the Uthat for safekeeping. When Picard learned, however, that it was two Vorgons who attempted to steal the Uthat in the first place, he destroyed it using Transporter Code 14, thus fulfilling his role in history. Failing in their quest to obtain the Uthat, Boratus and Ajur returned to their own time. (TNG: "Captain's Holiday")
Boratus, Ajur and the Tox Uthat return in Star Trek Online, in which they are approached by a figure known only as "the Envoy", who reveals that the Tox Uthat was in fact hidden at Starfleet Headquarters. Refusing the Envoy's offer to join his Temporal Liberation Front, the two Vorgons infiltrate Starfleet Headquarters during the Breen attack on Earth in 2375, pursued by Agent Daniels and the player character. After Ajur is killed by the player, a vengeful Boratus agrees to join the TLF, and participates in the Battle of Procyon V in the 26th century.