Power drain

The Power Drain is a short-range magnetic offensive weapon featured in Halo 3.

Function
The power drain creates a short-range magnetic induction effect which causes disastrous failure of powered field systems within a set radius, and is designed primarily to interfere with common varieties of 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, rendering them unable to move (or fire 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 a very short time after it is thrown - it has 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. In fact, it 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.

Spawns
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 side on Valhalla.

The Pit

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

Narrows

The power drain spawns right in front of the man cannon on each 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 centre 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.

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."
 * Although the Power Drainer disables the vehicle's movement, any armaments (etc. Scorpion turret, Warthog turret)on the vehicle will still work.
 * Sometimes throwing the Power Drain at UNSC forces can gradually drain their health over time, resulting in a kill before the explosion.
 * 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.
 * 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.
 * It may also be used as grenade by throwing it at a group of enemies then it drains their shield,after a while it will explode and sometimes killing the shieldless foes.
 * If a player throws a regenerator and a power drain at him self, the regenerator will have no effect and the player's shield will drain as fast as it usually would.
 * If a door is blocked by deployable cover a power drain with stop its ability to cover and it's is a good way to allow allied units inside a closed area
 * On the Halo 3 campaign, Brutes will occasionally use Power Drains.
 * On Valhalla try taking down banshees by tossing one into the Mancannon.
 * In the Campaign, it is possible to die from staying within the Power Drain's "field" (It will drain your shields then the explosion will kill you). However, in multiplayer, it cannot kill you, 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.