Overshield

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

Function
The Overshield technology is used by the Covenant to enhance their Elite warriors' shields by a factor of three. In Halo 3, these overshields only boost a player's shields to 200% (although, MLG's playlists have a Custom Powerup overshield that is of 300% strength). However it can also be used by any Spartan in Mark V or VI MJOLNIR armor who might come upon it. When picked up, it takes approximately three seconds to completely charge, but during the charging period the player will be invincible for five seconds after the overshield has been picked up. Once active the players normal shield does not take damage until the over shield is completely depleted (although any damage overlapping from something destroying the overshield, for example a grenade's explosion, will also do damage to the player's normal shield). If the overshield is picked up when the players shield is below 100%, the player receives a full charge and the effects of the over shield stay. In the single player campaign the overshield is reduced only when the player takes damage. In multiplayer, it gradually depletes over time.

Appearance
A glowing red (gold in Halo 2) orb of energy encased in a glass cube. In Halo 3 the orb appears to be held together by several small magnets. After walking over an Overshield, Master Chief's HUD shield display changes color from blue to red then green. Each color indicates one 'layer' of shields.

While wearing an overshield in Halo 2 and Halo 3, the MJOLNIR armor is surrounded by a glowing force field which is easily seen even when wearing the Active Camouflage. This does not happen in Halo: Combat Evolved.

On the HUD, the shield monitor shows a light green for a fully charged overshield, red for the second level, and the usual blue/purple (depending on player model) for the normal shields. The Halo: Combat Evolved overshield shows yellow at the highest level rather than green.

Advantages
Overshields effectively triple the strength of the MJOLNIR and Elite armor's shields (only double in Halo 3). The shields can now protect the user from heavy weapons such as Rocket Launchers, Fuel Rod Cannons, Sniper Rifles and even Plasma Grenades (unless stuck). Also, while the shields are charging you are immune to conventional damage but will still be vulnerable to assassination, falling to your death and the Guardians.

Disadvantages
Due to the bright glow of the overshields, the wearer is made more visible to other players, often drawing unwanted attention. In multiplayer, the overshield slowly loses its strength over prolonged periods of time, unless the player is a Juggernaut, VIP, or Grifball carrier. An overshield can be fully depleted by an overcharged Plasma Pistol shot.

Note: The glow does not appear in the Halo:Combat Evolved game, and therefore has no disadvantages. The glow was probably added to balance the power up.

Trivia

 * In Halo: Ghosts of Onyx the force of Elites that assaults the Spartan team in the portal chamber are described as being equipped with overshields, yet they seem to be just as easily killed as Elites with standard shields.
 * If you pick up an overshield and walk over another before the first overshield is fully charged, you will use up both overshields but only receive the effect of one.
 * The Overshield only appears in some Halo: Combat Evolved single player levels, it never appears in the single player levels of other games.
 * If you combine an overshield with an active camo, you will appear invisible but still with the glowing outline created by the overshield.
 * The first time they are seen is on the level Pillar of Autumn inside the Covenant boarding crafts.
 * An easy way to kill enemies with overshield it's by sticking them with a Plasma or Spike grenade.