Moving ahead of the main worldship convoy, the worldship was secretly ferrying members of the Praetorite Vong (as well as their yammosk) into the galaxy to begin the invasion ahead of schedule, so that the Praetorite Vong would be able to dictate the course of the invasion. The ExGal scientists at Belkadan tracked the worldship's vector to Helska IV.
Assuming the vessel was an asteroid, they were surprised when Helska 4 was not shattered when the "asteroid" entered the atmosphere. Danni Quee and two others decided to go and investigate the event. The worldship was presumably destroyed during the Battle of Helska IV.