Gravity lift

The Gravity Lift is the result of Covenant gravity-manipulation technology used to either consume objects into the ship's interior, or to safely transport troops to a surface. However, the polarity of the lift needs to be reversed in order to switch from the two different functions. They can be projected from both the underside of most Covenant ships and Deployable Lookout Towers.

Appearances
Gravity Lifts are seen twice in the game Halo: Combat Evolved. These scenes both involve the Master Chief and the Covenant CCS-class battlecruiser Truth and Reconciliation. The gravity lift belonging to the High Prophet of Regret is also seen in Halo 2, throughout the first few levels as it holds position over New Mombasa.

Gravity Lift as a Weapon
The gravity lift can also serve as a weapon. It was seen in the cutscene after Master Chief killed the Prophet of Regret in the Delta Halo Temple Lakes. Many people believe this to be an energy projector, although an energy projector is pure white and is mounted and placed onto multiple areas of a Covenant ship, which is unlike the gravity beam which is noticeably located in the same area as gravity lift. Also, to help prove the gravity beam is based off of the gravity lift. Look at the circumference of the gravity beam. It has the same exact shade of purple as the gravity lift as well as the oscillating lines on the outer wall. It is possible that the gravity beam is a gravity lift put into reverse on maximum power. This is noticeable as the gravity beam hits the floor of the temple it, the debris is forced downwards.