Sonaj was a Vulcan male working for the Federation Department of Temporal Investigations in the late 24th century.

In 2365, he was an experienced DTI field agent, who junior agent Marion Dulmur hoped to be partnered with for his first case.

By 2381, Sonaj had been promoted to Assistant Director of the San Francisco branch office.

In December of that year, he was at the Greenwich headquarters of the DTI for a meeting to discuss the opening of a new front in the Temporal Cold War directed at the present. (DTI novel: Watching the Clock)