The clash known as the Battle of the Emperor's Plague Storehouse involved the New Republic against the Diversity Alliance, a group of zealots opposed to Humans. The Diversity Alliance's goal was the complete eradication of all Humans as retribution for the Humanocentric actions of the Galactic Empire.
Before the conflict, Bornan Thul, the father of Raynar Thul and a prosperous shipping magnate, obtained a navicomputer. His assignment was to deliver it at a trade conference to Nolaa Tarkona, the leader of the Diversity Alliance. However, he discovered the navicomputer held the coordinates of an Imperial plague warehouse containing the Emperor's Plague, a plague specifically lethal to Humans. Nolaa Tarkona intended to unleash the Emperor's Plague in a genocidal anti-Human campaign, as revenge for the Galactic Empire's humanocentric policies and Ysanne Isard's Krytos virus (which was not species-specific, but greatly impacted the alien population of Coruscant after the New Republic liberation in 5 ABY).
Terrified and seeking safety, Bornan went into hiding. Tarkona then engaged bounty hunters, including Ailyn Vel disguised as her father Boba Fett, to locate him. Bornan evaded capture for several months, eventually visiting the plague warehouse intending to destroy it. However, he lacked sufficient resources and was forced to abandon the mission. On his return, bounty hunters ambushed him, damaging his ship.
After Zekk's ship, the Lightning Rod, rescued him, Bornan revealed that Ailyn Vel had accessed his ship's navicomputer and acquired the plague warehouse coordinates. Bornan recorded an encrypted message for his wife explaining their plan. Then, accompanied by Raynar, Zekk, Jacen and Jaina Solo, Tenel Ka, Em Teedee, and Lowbacca, Bornan gathered explosives and headed to the warehouse with the intention of destroying it.
Their wiring work was nearly complete when Diversity Alliance ships appeared. During the subsequent confrontation with Tarkona inside the warehouse, some of the plague canisters were breached, releasing the Human-specific plague. Bornan sacrificed himself to contain the plague's spread, instructing Raynar to evacuate himself and his friends from the asteroid. Also, during the conflict, Lowbacca engaged the Trandoshan Corrsk in combat, resulting in Corrsk's death.
Simultaneously, a New Republic fleet commanded by Han Solo arrived in space and engaged the Diversity Alliance ships. The New Republic fleet triumphed over the Diversity Alliance fleet, which was under the command of the Wookiee Raabakyysh. Following this victory, they destroyed the plague storehouse, eliminating the biological weapons cache. This marked a significant victory for the Jedi and the New Republic, leading to the defeat of the Diversity Alliance. However, Nolaa Tarkona escaped, eventually succumbing to a Twi'lek-specific virus on a remote asteroid.