Doctor Tolian Soran was an El-Aurian scientist, born around the late 21st century. He was over 300 years old by 2371. During the Borg assimilation of 22nd century, all of Soran's family was killed, including his wife, Leandra, and their children. Soran survived the assimilation and escaped with thousands of other refugees. (ST website: Startrek.com)
In 2293, Soran was being transported to Earth with hundreds of other El-Aurian refugees aboard the Federation transport Lakul. A few light-years out from Earth, the Lakul encountered the Nexus energy ribbon and Soran entered the Nexus and was greeted with his greatest dreams and desires. Unfortunately, he was ripped away from the dreamworld and beamed aboard the Excelsior-class USS Enterprise-B.
Unlike the other El-Aurian refugees, Soran couldn't come to terms with the fact that the dreamworld was gone, and spent the next 78 years formulating a plan to re-enter the Nexus. Obsessed with the passage of time, he kept an antique Terran pocket watch on his person at all times. His constant reminder, however, brought about his death as he was stopped by the combined efforts of Captains Picard and Kirk. He did succeed in an alternate timeline and it resulted in the destruction of the Veridian system and all hands (except for Picard) of the Enterprise-D. (TNG movie: Star Trek: Generations)
In 2384, when Picard ventured back into the Nexus, a remnant of Soran helped him achieve his goal of locating a Federation scientist. The Styrisian scientist who had entered the Nexus did so without authorization and left after causing an explosion aboard a Federation starship. This led to Picard entering the Nexus to go after him, who later sought help locating the Styrisian. Picard encountered Soran sometime after he entered, but this was only a mere remnant that he found. The remnant himself lived on a beach with his family, surrounded by many other El-Aurians. The remnant was vastly different from the Soran encountered by Picard and his crew, offering his help without cost and greeting Picard like an old friend. (TNG novella: The Stuff of Dreams)