Gravity Well Generator

The Gravity Well Generator was a device of Forerunner origin that was used to artificially create a Gravity well. One such device was located on the Forerunner Shield World of Requiem. The Gravity Well Generator on Requiem was used to pull the wreckage of the UNSC Forward Unto Dawn, several Covenant ships, and later the UNSC Infinity into the planet. The device was later destroyed by the crew of the Infinity with the help of John-117 and Cortana.

Function
The Gravity Well Generator was a massive device that functioned to create an artificial gravity well that could be used in order to capture ships that were approaching the planet Requiem. Once caught in the gravity well, any ship or object would then be pulled into one of the giant entrance appetures that lead into the outer shell of the planet. The device could then be used to prevent these captured ships from leaving the planet.

First Battle of Requiem
The Gravity Well Generator on Requiem was used to pull the wreckage of the UNSC Forward Unto Dawn along with several Covenant Remnant ships into the planet after John-117 was scanned by the planet and identified as a Reclaimer. Later the UNSC Infinity, which was tracking the Forward Unto Dawn's distress beacon, was also pulled in. In order to escape the planet the crew of the Infinity dispached a Mammoth as well as several Pelicans to destroy it in order to allow the Infinity to escape. Despite being defended by several groups of Covenant and a battery of Forerunner Particle Cannons, the Infinity was able to destroy the Gravity Well Generator and escape Requiem.

Trivia

 * The Gravity Well Generator's use is similar to the use of the Tractor Beam technology seen in many other science fiction series such as Star Trek and Star Wars.
 * The Millenium Falcon is drawn into the Death Star's (another giant metal planetoid) hanger bay in a similar manner.