The initial Yuuzhan Vong worldship to penetrate the galaxy at Vector Prime was the worldship commanded by Prefect Da'Gara.
This worldship, preceding the primary worldship convoy, was covertly transporting Praetorite Vong members (along with their yammosk) into the galaxy. This was done to initiate the invasion prematurely, allowing the Praetorite Vong to control the invasion's direction. The ExGal researchers stationed at Belkadan monitored the worldship's trajectory, which led to Helska IV.
Initially mistaking the vessel for an asteroid, they expressed astonishment when Helska 4 remained intact despite the "asteroid's" atmospheric entry. Danni Quee, accompanied by two others, resolved to examine the occurrence. It's believed that the worldship met its end in the Battle of Helska IV.