This lore can be found by an Inquisitor on Tatooine.
Incidents of Sith Lords imbuing their most precious possessions with some fragment of their dark power appear throughout Sith history. Such ritual imbuement can be used to inflict all manner of trouble on those who would steal these terrible treasures. The Dark Lord of the Sith Tulak Hord was especially known for this practice, and many possessions of Tulak Hord’s have driven their discoverers to madness throughout the years. Tulak’s Madness is unique in who it affects, however; ignoring whether a person’s spirit is dark or light, it afflicts only the weak-willed, driving them to delusions of grandeur and eventual self-destruction.