An Overshield is a form of Covenant-developed technology that strengthens the energy shielding system of the user.
The Overshield technology is developed by the Covenant to enhance their Sangheili warriors' personal shielding system. The Overshield can be used by anyone utilizing a personal shielding system such as a SPARTAN in a MJOLNIR armor or Sangheili with a combat harness.
In Halo: Combat Evolved and Halo: 2, the overshield boosts the player's shields to 300%. This was reduced in Halo: 3; the overshield only boosts a player's shields to 200%. It takes approximately three seconds to overcharge the energy shields once picked up. During this short period, the player is invincible. The player's normal shield does not take damage until the overshield is completely depleted (although any damage overlapping from something destroying the overshield (i.e. a grenade's explosion) will also do damage to the player's normal shield).
In campaign mode, the overshield is reduced only when the player takes damage. In multiplayer, the overshield is not only subjected to the same rule in campaign mode but it will also gradually depletes overtime.
In Halo: Combat Evolved, the Overshield appears as a glowing red orb of energy encased in a clear glass cube. The same design is used in Halo: 2; this time, however, the orb and cube are gold in color. The design of the Overshield in Halo: 3 differs and shares some resemblances from previous titles: the orb appears as a glowing red orb of energy, without a glass cube encasing it.
After picking up an Overshield in Halo: Combat Evolved, the player's HUD shield display changes color from blue to red to yellow. The same is present in and Halo: 2, though the shield display changes color from blue to red to green instead of yellow. In Halo: 3 however, the shield display only changes from blue to red. This gives the indication that each color represents one layer of shield. A visual effect that is present only in Halo 2 and Halo 3 is the glowing effect which surrounds the user with an Overshield. This visual effect also negates the camouflage ability.
The Overshield can only be found in campaign mode in Halo: Combat Evolved. It is absent from Halo 2's and Halo: 3's campaign mode. In Halo: 3's campaign mode, a piece of equipment called the Invincibility replaces the Overshield. The Overshield makes an appearance in Halo 3: ODST as a shielding effect awarded to those within the vicinity of a Covenant Engineer; Covenant and UNSC units are provided an additional layer of protection because of the Overshield ability.
The Overshield effectively triple the strength of any shielding system in Halo: Combat Evolved and Halo 2, and double in Halo 3, Halo 3: ODST, and Halo: Reach. The Overshield can protect users from a direct fire of a Fuel Rod Gun, Sniper Rifles, Fragmentation Grenades and the Covenant Beam Rifle, and from indirect fire of a Rocket Launchers and Plasma Grenades.
When the overshield is activated during Halo: Combat Evolved's Campaign mode, the overshield will continue to stay active until the user takes enough damage, enabling the user to make certain falls without injury
During the three seconds of charging directly after picking up the Overshield, users are granted a brief moment of invincibility.
A Overshield user is susceptible to an assassination. Due to its reductive nature, the Overshield is only useful for a short period in multiplayer; the overshield slowly loses its strength over prolonged duration. Like the standard energy shield, the overshield can be fully depleted by an overcharged Plasma Pistol.
In Halo 2 and Halo 3, the wearer is awarded a visual effect which gives off a full-body glowing effect. This visual effect negates the effects of a camouflage ability and makes the wearer more visible to other players, often drawing unwanted attention.
- The Black Eye Skull allows the player to achieve overshields through meleeing enemies which restores the player's shield, though only in Halo 2's campaign.
- In Halo 3, you can pick up the overshield (or Active Camo) as equipment if you have a piece of equipment and hold your equipment change button (default RB) and barely touch the overshield. Then if you die you drop the Overshield, or if you pick up another piece of equipment you will drop/pickup the overshield, allowing you to surprise your enemies, this works on matchmaking online.
- In Halo: Combat Evolved, when you walk over an overshield, your screen will turn pink for a second and you will hear the same sound as when your shields are loading.
- The overshield was most likely inspired by a similar device found in the Marathon series. Using this device in the Marathon Series causes up to two additional layers of heath to be added (yellow/purple).