The homeworld of the Mazarites, from which the Vulcan ambassador V'Lar was expelled in disgrace.
Mazar is the world of the Mazarites. The Vulcan ambassador V'Lar served there until she was accused of misconduct and expelled, and in Fallen Hero Enterprise is asked to carry her home while Mazarite ships pursue them.
The journey reveals that V'Lar was in fact working to expose corruption within the Mazarite government, and the pursuit is an attempt to stop her. Mazar is mentioned again in Affliction, where the Klingon scientist Antaak attends a medical conference disguised as a Mazarite.