a bio-engineered form of capital ship, the Yuuzhan Vong worldship was created from a community of yorik coral. Known to the Yuuzhan Vong as a Koros-Strohna, these ten-kilometer-wide ships were living creatures designed to cross vast distances of space. Each was propelled by a collection of dovin basals, which could lock onto a nearby gravity source and use it to "pull" the worldship toward it at incredible speeds. A series of bio-engineered, membranous creatures were attached to the worldship, and could be extended whenever there was no strong gravitational field for the dovin basals to lock onto. The membranous creatures allowed the worldship to be pushed by the interstellar winds. Each worldship carried a compliment of coralskippers for added protection, and several were used to keep the membrane creatures extended. Because the worldship was a self-contained living environment, many Yuuzhan Vong inside began to go mad from the confinement. To ease this situation, special drugs were released into the atmosphere inside the worldship, to calm the Yuuzhan Vong population. Once the worldship was ready for landing, a huge, tubular worm was extended from the craft into the surface of the landing area, allowing the Yuuzhan Vong to establish a planet-side base and maintain contact with the worldship. Like all living creatures, worldships had to be regularly fed and nourished in order to maintain their systems, a chore which was carried out by the Shapers of the Yuuzhan Vong. However, also like living creatures, these huge ships eventually aged and died. Many of the worldships used by the Yuuzhan Vong to cross the intergalactic gulf were quite old by the time they reached the New Republic, having traveled through the intergalactic gulf for many generations, and many began to die shortly after the invasion began.