Luminary

A Luminary is a Covenant technology, modeled and sculpted after a Forerunner device recovered from the Covenant-controlled Forerunner Dreadnought. Its purpose is to scan for and identify Forerunner relics and is required on all Covenant vessels. It is described as a series of three silver pyramids: two smaller ones supporting an upside down larger one in the center. There are apparently several models of Luminaries, more advanced versions (presumably a better reconstruction of the original Forerunner devices), as it is revealed primitive versions of Luminaries lead the Covenant to discover the Lekgolo, shortly after the formation of the Covenant. Luminaries are of great religious significance to the Covenant and tampering with them was punishable by death. A Holy Writ, essentially the Covenant equivalent of folk wisdom, concerns the Luminaries, namely, "A Luminary does not lie."

As the presence of a Luminary is required on all Covenant vessels, there are likely at least tens if not hundreds of thousands of them in existence, depending of course on the number of ships the Covenant control. The Luminary of the Minor Transgression is significant as it led the Covenant to the UNSC colony Harvest, and precipitated the Human-Covenant War. It identified Harvest with several thousand Forerunner glyphs (referred to as Luminations in this context and called relics by the Covenant) that led the Covenant to believe the world held innumerable Forerunner treasures. Unfortunately, they misinterpreted the sign as "Reclamation," rather than the actual translation, "Reclaimers."

Trouble with the Covenant
Although the newly appointed Prophet of Truth was aware of the mistake caused by this "misinterpretation", he refused to let the Covenant know of the human ties with the Forerunner and instead uses this as motivation to begin the Human-Covenant War in order to ensure the survival of the Covenant, as the very basis of their faith is that there are no more Forerunners alive. Instead, he claimed that the Luminaries were all incorrect. As a result, he claims that the "filth" were out to destroy the holy Forerunner relics and most importantly, the Halo rings. He also planned to use this as a means of getting the location of all the humans so he could exterminate them.

Trivia

 * In The Covenant, the punishment for tampering with a Luminary is death.