Koros-Strohna, known as worldships in Galactic Basic Standard, were immense spacefaring vessels that housed entire communities of the extra-galactic Yuuzhan Vong, providing them with food and shelter. The worldships also served as staging grounds for more arduous battles or confrontations. As Yuuzhan Vong culture and religion professed a deep-rooted, zealous condemnation of any "modern" technology, such as droids, advanced computer systems, electronics or nuclear power (among other concepts), their worldships were always built from organic materials. Many vessels were constructed from and/or powered by functioning organisms, such as yorik coral or other living invertebrates.
Similar, in function, to the reborn Emperor Palpatine's Eclipse-class Super Star Destroyers, a worldship was a combination of a community, battleship, psychological weapon, and form of transportation, all-in-one.
A Koros-Strohna amid the Yuuzhan Vong fleet
Like all other Yuuzhan Vong technology and vessels, the Koros-Strohna was built of yorik coral. This coral then formed symbiotic relationships with many other organic materials and organisms utilized in a vessel's construction to provide defense, propulsion, and arms capabilities. Maw luur served as a recycling system as well as provided valuable life-support to the vessel. A worldship had more in common with a living planet than a starship, and, like most other Yuuzhan Vong bioengineered vessels, did not appear to be a spaceship, at all. The ship's core section was a disc-shaped mass, covered with hundreds of projectile defense mechanisms, among other protrusions. Around the middle edges of the worldship were several large, spiraling "arms", giving the vessel the vague shape of a spiral galaxy or a hurricane. In areas where gravitational pull was weak, such as the voids between galaxies, the Koros-Strohna could extend numerous membraneous "tendrils" called outrider ganglia, with each membrane anchored by hundreds of coralskippers, or yorik-et, smaller, similarly coral-based "starfighters" which were operated to help unfold the membrane. Once unfurled, the ganglia served as cosmic sails.
Dovin basals propelled the worldship by projecting gravity wells to drag Yuuzhan Vong ships through the interstellar void. When these organisms concentrated their energy wells, they could cause a space station to collapse entire worlds or moons, even forcing a binary system to collide. Dovin basals could also strip enemy vessels of their deflector shields. The worldship's own defenses also relied on the dovin basals' ability to utilize gravitational wells when intercepting incoming enemy fire or other potential assaults. To conserve power, worldships could generate artificial gravity by rotating, thus preserving the dovin basals.
The Domain Hul worldship at the Battle of Borleias
Worldships were protected by hundreds of yaret-kor emplacements that spat molten "slag", or magma, at enemy vessels. These ranged from starfighter-sized cannons to turbo laser-sized weapons similar to those used by the New Republic. These magma-based weapons ranged from small openings with the capability of blaster cannons to larger emitters which could shoot massive volcanic boulders, up to the size of a small starship, over great distances. The Koros-Strohnas weapons were spaced sporadically, and recharged slowly as new magma was produced; these firearms proved fantastically accurate, despite their unconventional creation.
Another weapon was a huge, tubular worm called the dread weapon, which extended from the bowels of the worldship. The dread weapon could be used to gather nutrients for the worldship to stay alive. The Gorros' Fen served a similar function.
Additional defenses came from the worldship's cargo and troop holds, which could transport more than 5,000 warriors, along with coralskippers and terrestrial ground vehicles. Due to the vessel's size, the Koros-Strohna would often accommodate a small Yuuzhan Vong army.
A Yuuzhan Vong worldship lived and functioned for a minimum of 500 years, if not longer, as they were known to operate for up to 1,000 years, as the Baanu Miir proved. As a worldship started to near the end of its life, it would develop color variations on its dovin basals, and would grow myogens in its corridors.
In 26 ABY, the worldship Baanu Miir held twelve thousand Yuuzhan Vong, and was nearly 1000 years old (an age considered ancient), dying and no longer able to travel faster than light. It is unknown if these figures were typical for worldships. The Baanu Rass, one of the largest worldships, was 120 kilometers across, almost the size of the first Death Star. During the trek through the intergalactic void between galaxies, certain drugs were circulated into the worldship's interior, which infused its inhabitants with a sense of purpose and belonging in order to prevent them suffering mental breakdowns resulting from the stresses of a long journey across space to the Promised Land.
The Alak Schou was one of the worldships used to transport the invasion force into the galaxy. The Domain Hul worldship served as a base for the Yuuzhan Vong assault against the New Republic during the attack on Borleias.
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