Kali was once his faithful servant, acting as his ashrak and killing any who her master deemed fit. Because of the dominion he held, he was given access to the Tau'ri of Earth by Ra soon after they were discovered. Despite this fact, Shiva refused to leave his Unas host; a fact which worried his ashrak, Kali, as it meant that the Tau'ri often thought of Shiva as a demon rather than a god. Though Kali made her master aware of this, and the potential it had for inciting unrest, the fact satisfied Shiva who refused to unblend from his Unas host.
Ra shared Kali's concern and soon arranged for a meeting between himself and Shiva where he was going to demand that, as long as Shiva continued to make use of the Tau'ri slaves, he had to take a Human host. Shiva defied the Supreme System Lord, however, and chose not to even attend the meeting; instead, Kali appeared in her master's place looking for a way to divert the bloodshed which she knew would be caused by Shiva's defiance.
Ra, furious at Shiva's insolence, had other plans; instead of offering a compromise he demanded that Kali kill her own master. Though Kali was loathe to do this, she recognized that it was the only way as, if Shiva did not die by her hand, then he would surely die by another's. Ra further sweetened the deal by claiming that he would take Shiva's territory for his own once Kali had killed her master and would allow Kali to rule over it in his stead as his subordinate; Kali agreed, and struck down Shiva. (SG1: "Kali's Wrath")