Duke Horis Thul was a male Human hailing from House of Thul and lived during the era known as the Cold War.
In the year 3643 BBY, Duke Horis Thul voiced his support for the peace negotiations that were being proposed by Duke Charle Organa; the assassination of Thul by a Republic superweapon would have resulted in the collapse of the peace process. He then crossed paths with the Hero of Tython, who had arrived with the purpose of rescuing Horis. Aleyna Hark gave the order for the duke's guards to initiate an attack, claiming that the Jedi had arrived to kill Thul and to undermine the alliance she was working to establish. However, the Knight was able to defeat Hark and the guards, and subsequently managed to persuade the duke of Hark's deceit. When the duke and the Jedi demanded the targeting device, Hark vindictively destroyed it and revealed that she had marked them too. At that moment, Thul responded by punching Hark in the jaw, rendering the Mirialan unconscious. He then disclosed that he had been monitoring Nefarid, in the event that the Sith were to betray House Thul, and he proceeded to provide the Jedi with Nefarid's location. Before making his escape toward the spaceport, the duke insisted that Aleyna be put to death, but the Knight was successful in convincing the duke to instead have her arrested and subjected to a trial. Wynne Organa later informed the Knight that Thul had handed Aleyna over to House Organa as a gesture of goodwill.
Horis later communicated a message to the Hero, expressing his gratitude and explaining that his interrogation of Aleyna had unearthed Imperial spies within his house.