Covenant rope

The Energy Tether is a device used by Covenant soldiers to rapidly descend from high places, as seen in Halo: First Strike. They work similar to grappelling rope, but are made of pure energy.

Operation
It is unclear how the ropes are kept together or how they are powered, but they appear to work just as well as normal rope without causing rope-burn. It is most likely a small but extremely powerful Gravity Lift. These ropes are most commonly used by Elites and Jackals.