Threnody

Threnody (also known as Shield 0927) is a Forerunner Shield Installation in the Gamma Serpentis system. It was originally intended to protect sentient lifeforms from the effects of the Halo Array and the Flood however it was never completed by the Forerunners and remains a dormant shell monitored by 823543 Adjudicator Sentry and a handful of sentinels.

Discovery
In 2554, a single United Nations Space Command corvette, the UNSC Adamstown exited slipspace in orbit above the installation on a mission to locate Forerunner shield installations. Upon arrival the crew flagged the discovery and contacted the Office of Naval Intelligence.

A day later and a Valiant-class super heavy cruiser, the UNSC Kilimanjaro arrived to investigate the shield world. Several incomplete entrances to the shield world were discovered allowing the cruiser to enter the shield world easily. The Kilimanjaro deployed two UNSC prowlers to investigate the planet on there own before exiting the planet and entering slipspace.