Yost was a member of an unnamed species native to the Delta Quadrant. In 2375, as the supervisor of Renovation Team Nova, he was ordered to seal a subspace sinkhole which had claimed a number of ships.
This proved a problem for the crew of the USS Voyager, who were attempting to retrieve Tuvok, Tom Paris, and The Doctor after their shuttlecraft was pulled into the sinkhole. Yost was unwilling to adjust his schedule for their rescue attempt and even began to seal the rift early, though Voyager was able to rescue their people in time. (VOY: "Gravity")