The Yoke of Seeming, a Sith artifact, existed even before the Dark Jedi Exiles arrived. XoXaan took possession of it. Legend had it that this artifact could transform the user's appearance into anything or anyone, but this transformation came at the cost of burning the user's skin.
Sometime later, Haazen obtained the artifact and integrated it into his cybernetic enhancements. This integration substantially enhanced his link to the Living Force and gave him the ability to obscure the perceptions of other Jedi, thus concealing his real motives. Beyond just hiding his intentions, the Yoke also broadcasted Haazen's desired self-image to all Force-users. As a result, while other Jedi could visually perceive his actual, disfigured appearance, their reactions were less intense. Haazen could also lessen its effects at will, as he demonstrated during a conversation with Lucien Draay, a moment when he aimed to project a sense of disgust.