Testament Day was a holiday in the Lost Tribe of Sith society. It was held every twenty-five years on the day of anniversary of the Tribe's first Grand Lord, Yaru Korsin's death, in the office of the Caretaker. It consisted of a lecture of the final testament of Korsin in person.
- Lost Tribe of the Sith: Pantheon (First appearance)
- Lost Tribe of the Sith: Secrets (Mentioned only)
- Lost Tribe of the Sith: Pandemonium (Mentioned only)