The conflict on Yn involved the Sith Empire clashing with forces composed of Jedi and rebel fighters, all opposing the Sith Lord known as Tulak Hord. During Hord's military actions on the planet Yn and the Jedi-controlled Chabosh, he refused an alliance offered by Sith Lord Aloysius Kallig to fight alongside him. Following Kallig's killing of Hord's primary general, Hord permitted the other Sith to command his armies, resulting in several victories.
Around 5300 BBY, when the Jedi launched an assault on a Sith fortress located on Yn, Tulak Hord, along with his apprentice, Ortan Cela, and their Dashade Shadow Killers, Khem Val and Veshikk Urk, spearheaded a military force of warriors aligned with the dark side to relieve the Jedi's siege. They successfully eliminated the Jedi and the rebels who stood against the Sith Empire's expansion. Urk and Val consumed the Force potential from their defeated foes, while Tulak Hord employed a ritual to absorb the life force of his enemies, enhancing his own strength and vitality. After securing victory in this engagement, Hord then directed his armies to seize control of Chabosh.
Around 3643 BBY, Khem Val would reminisce about Tulak Hord and his successful subjugation of Yn and Chabosh to the Sith Inquisitor whom he served, who was a descendant of Kallig, occasionally referring to both himself and Hord as the "conqueror of Yn and Chabosh."
The first mention of the battle of Yn occurred within Khem Val's profile on the Holonet section of the BioWare video game, Star Wars: The Old Republic's official website in 2011. Should the Sith Inquisitor player character opt not to aid Khem Val during the "The Escape" mission, which takes place around 3643 BBY on Taris, the Dashade would express approval of this non-intervention. He would then forcefully expel Darth Zash's spirit from his own body and trap it within a mind prison created by the ancient Rakatan civilization, declaring triumphantly that he served Tulak Hord, "conqeuror of Yn and Chabosh."