Overshield

Overshields are a form of Covenant developed technology that strengthens the Energy Shields of the user.

In-Game
In Halo Origins, Overshields are required for the following Covenant infantry units: They require 20 Crop, 15 Minerals, 10 Steel, 35 Iron, and 15 Credits to build per unit.
 * Jackals
 * Elites
 * Prophets

Picture
http://images2.wikia.nocookie.net/halo/images/thumb/8/82/Overshield.jpg/180px-Overshield.jpg