Yorik-tremas resembled a bloated mass of molting tissue. Like the rest of Yuuzhan Vong technology, the vehicle was actually a complex organism. Whenever a planetary invasion began, hundreds of these craft were released from Koros-Strohna Worldships or other warships. The transports then fell rapidly towards the planet's atmosphere, descending in a straight line as if simply dropped.
Because of their unusual landing pattern, the New Republic military labeled them "crates." As it descended into an atmosphere, the yorik-trema was protected by a thick shell from artillery fire covering its ventral surface. The shell was ablative and would wear away under heavy fire, however it also had regenerative properties and could heal quickly, even when under attack.
Yorik-tremas were often escorted by several coralskippers but they were not unarmed. When attacked, the yorik-trema sprouted a pair of hornlike projections that were actually weapons capable of firing damaging plasma bolts at planetary weapons emplacements and even small, swift starfighters. The yorik-trema possessed several sensors that tracked the movements of its escort coralskippers and could also quickly identify enemy craft. These sensors resembled large, alien eyes.
Each yorik-trema was divided into two sections. The forward section had only enough room for a pilot and a commander while the large rear section held up to 30 slave soldiers, mainly Chazrach, along with 6 full-fledged Yuuzhan Vong warriors. The yorik-trema could also carry vehicles. For landing, the yorik-trema had several sharp claws capable of landing on any terrain, even on rocky cliffs, snowy plains or buildings.
Once the vehicle landed, the yorik-trema used several hollow molleung worms that extended from its sides. These worms served as disembarking tubes for the soldiers, who poured onto the battlefield. The molleung worms were also living creatures that could lash out at enemy troops to clear a landing zone. The yorik-trema could also attach to enemy ships, where it chewed a large hole in the vessel's hull. Once the hull was breached, the Yuuzhan Vong soldiers could easily board the enemy ship and wipe out resistance.
The yorik-trema transport carriers were first encountered by the New Republic during the Battle of Ithor. One of the yorik-trema launched at Ithor carried Commander Shedao Shai to the surface, though he was killed in combat by Corran Horn.
Throughout the Yuuzhan Vong War, the yorik-trema were used in many battles, and one such vessel was even assigned to the Supreme Overlord Shimrra himself. Located within his coffer - his escape vessel - the yorik-trema actually provided a means of escape for the heroes of the Galactic Alliance, after the defeat of Shimrra and Onimi. Though the yorik-trema was slowly dying, the heroes were rescued by the Millennium Falcon in time.