Power drain

The Power Drain is a short-range, tactical, energy sapping device featured in Halo 3.

Function
The power drain creates a short-range Electro Magnetic Pulse (EMP) effect which causes disastrous failure of powered field systems within a set radius, and is designed primarily to interfere with common varieties of electrical field-based shielding, vehicle and power generation. It also has a damaging effect on biological systems and can wound or kill most bipeds in its resulting explosion. Essentially, the Power Drain is like a reverse Regenerator; instead of energizing a player's shields, it causes any player's shields within the area of effect to drain away, making them vulnerable to harm. The self-destruct explosion after the activation of the Power Drain will not kill you (If you were at full armor health previous to deploying it), but will take your health to critical levels. The Power Drain can also disable vehicles via EMP, rendering them unable to move (but the vehicle can still use and aim its onboard weapons) when they drive or fly through it and even about 5 seconds afterwards. If a Regenerator and Power Drain are deployed in close proximity, the Regenerator will stop working.

The Power Drain, like the Bubble Shield, Trip Mine, Radar Jammer and the Portable Gravity Lift, are all in the category of equipment and can be deployed using the "X" Button. It activates shortly after it is thrown - just enough inactive time to travel away from the user, leaving them unaffected.

The power drain can even disable non drivable vehicles like the Scarab as seen in TGS Demo Part 2, but the weapons systems will still be active, as in any vehicle. In fact, the power drainer will affect any device that runs on any type of energy within its radius in game.

Tactics

 * In both Campaign and Multiplayer, this is an effective vehicle-annihilator, provided that you don't stand too near to it when it is active and lively.
 * This equipment may stall a vehicle's engine, but the turret on the vehicle still works, working quickly with the Power Drain and a weapon or grenade is the only smart way to kill everyone inside a turret vehicle.
 * This is a good piece of equipment that is well used in conjunction with headshot weapons such as the Battle Rifle and Magnum.
 * This is the piece of equipment that is a must need when outnumbered, once drained, the whole group becomes a big one-shot target.
 * Bubble Shields cannot block the Power Drain from entering, so it's a good idea to throw one inside of a Bubble Shield while your enemies are inside of it. Also the effects of the Power drain will be blocked by the Bubble shields walls and vice versa.
 * One of the most annoying things is being stuck inside one of these fields or having to go through one to get to your enemies. Shoot to take out the Power Drainer's contraption to get to your enemies. This is a quick and effective way of getting rid of them and annoying your opponents even more at the same time.
 * Try to deploy it near a popular sniper position or an area where people land after they get off of a Grav Lift.
 * Whilst the Power Drain affects the Spartan and Elite player and depletes their shields entirely the Bubble Shield does the just opposite, protecting the player from any known projectile... the two parallel each other in effectiveness and usage.
 * Very effective at capture the flag, when the opposing team grabs the flag a power drain leaves them and any other players on one hit kill.
 * Try and keep a distance from you and your foe when in combat online, as when in close quarters battle (CQB), they tend to use power drains
 * Activating a Regenerator inside power drain's drain radius would cancel out the drain effect. However the power drain can also negate the Regenerator, making it easier to kill people inside Regenerators.
 * Can take out brutes shields thus making them easier to kill.
 * On Construct toss a Power Drainer into the yellow gravlift followed by a couple of grenades to get easy kills.
 * While it is pure luck when it happens, it is possible to splatter an opponent with a Power Drain by tossing it down a hill and it hitting them while it is rolling.

High Ground
The power drain can be found on a small metal ledge inside the main compound of the High Ground base. The ledge is within jumping distance of the flag spot.

Snowbound
The power drain spawns inside "Low Base" on Snowbound.

Valhalla
The power drain spawns near the center man cannon at either base in Valhalla.

The Pit
The power drain is located in the center of the map, on the bridge connecting the upper level to the sword spawn (between each base).

Narrows
The power drain spawns right in front of the man cannon on the gold side of the map.

Last Resort
The power drain is found on the small set of stairs in the back corner of the main base.

Construct
The power drain can be found in two places; the first is at the bottom of the yellow gravity lift to the top of the map, the second is next to the sword spawn on the enclosed catwalk on the top level.

Sandtrap
The power drain is found inside one of the buildings with an air vent in the center of it.

Epitaph
The power drain is located behind the gravity lift that sends you to the rocket launcher spawn point.

Standoff
The power drain can be found at the bottom room of each base, opposite to "Gate Switch".

Foundry
The power drain can be found up the ladder of where the red team starts normally (on the default Foundry map).

Avalanche
The two power drains are located at the base of the mancannons that take you inside a base.

Blackout
The power drain is located on the floor under the helipad, right by the hole that drops you down to the shotgun.

Trivia

 * It shares many physical similarities with the Radar Jammer and Flare, with exception of a blue glow instead of a red/yellow glow.
 * It is also capable of draining vehicle power as well, causing the vehicle to stop in its tracks or malfunction. If a vehicle gets in the radius of the drainer for even a brief moment they would lose control of the vehicle. A Bungie employee remarked that "the guy" he just boarded used the Power Drain to once again disable the Banshee."
 * In the Multiplayer Beta, the players got the Power Drain and the Bubble Shield mixed up and ended up dying or shielding the enemy player. The Beta version when deployed, was a glow of a much lighter blue color and had a larger effect radius which had a cloud of haze around the edge.
 * A fun and weird thing to do is throw down a Bubble Shield and then throw a Power Drain in it and the effect will be contained, like explosions, but the glow will still reach out.
 * When the Power Drain is thrown at the generator of a Bubble Shield, the Bubble Shield will actually move over a few inches when hit by the Power Drain.
 * It may also be used as a grenade by throwing it at a group of enemies draining their shields and after a while the resulting explosion can sometimes kill the shieldless foes.
 * On the Halo 3 campaign, Brutes will occasionally use Power Drains.
 * On Construct, if someone throws a Power Drain into the main gravlift, if you then go through it, the power drain at the top will levitate you off the floor and throw you to your doom.
 * In the Campaign, it is possible to die from staying within the Power Drain's "field" (It will drain your shields and the explosion will kill you). However, in multiplayer, it may kill you at a certain point (If you have received some damage, it is possible), but it will still drain your shields.
 * The Power Drain can be thrown through the shield doors on all levels and through a deployed Bubble Shield. This is a very efficient way to root out campers.
 * Even after rendering a vehicle unusable, its engine is still 'affected' by the Power Drain.
 * If you fire a Spartan Laser while near a Power Drain and view the beam in Theater mode from within the Power Drain's field, the beam will be a blue-white color.
 * A common strategy on Valhalla involves throwing the power drainer out the man cannon to intercept a low flying Banshee. The Power Drainer's relatively large damage radius will normally result in the disabling of the banshee's engines for about 5 seconds, during which it can be destroyed/boarded.
 * The effects of the Power Drain can also pass through walls and floors so simply jumping to the floor on the bottom after an enemy activates one may still strip your shields through the roof if you pass through it.
 * When combined with the Regenerator, your shields glow due to the conflict of effects.