The Prion Empire

Prehistory
The Prion Empire is an ancient race that predates the Humans and possibly the Forerunner. The only records that could have possibly held information on the pre-Forerunner Prion Empire were the records kept by the Precursors, which were mostly, if not entirely, destroyed by the Forerunner.

One artifact, however, had survived from the pre-Forerunner era of the Prion Empire named the Umbral Enigmaton due to its dark shade and the lack of knowledge behind its function or purpose.

The Forerunner
Few records have been found that describe the Prion Empire and its interactions with the Forerunner. However, one very detailed text recovered by Ares Team contains the information on a brief war on the Forerunner, such as this sample:

"...the Prion do not have a stable army. Most of their population is technicians and researchers, but I must admit they handle plasma technology well. However, they have no tactical experience or combat efficiency. Sometimes I wonder how few Sentinels it would take to wipe one of their cities from the planet. Pilox keeps telling me not to underestimate them, but he's never had to fight them. He doesn't know how fragile they are; physically and mentally."