Energy Ball

An Energy Orb is a concentrated sphere of dark energy plasma, a form of exotic matter that disrupts spacetime and distorts light.

Overview
Energy orbs are generated by Combine dark energy reactor systems and transmitted through the plasma conduits of Citadel power transfer systems. Energy orbs can be contained within specialized dark energy cores, portable long-term storage devices that can later be used in Combine dark energy devices. As well as power generators, dark energy cores can be plugged into the Overwatch Pulse Rifle, which can store the energy until released by the rifle's secondary fire.

Energy orbs repel themselves from matter of sufficient mass and density, bouncing off of walls, ceilings and floors without losing inertia. However, when they strike matter of low density or mass, they are destroyed, causing them to dissolve into nothing. Gordon's HEV suit, being plated, may explain why the player will sometimes deflect the orb rather than absorb it upon impact.

Energy orbs are subject to zero-point energy fields, allowing them to be grabbed and manipulated by the gravity gun.

In Portal, the "Aperture Science High Energy Pellet" bears a remarkable resemblance to the energy orb, therefore suggesting that Aperture may have created a dark energy system of their own. However, unlike the energy orb, the pellet is not subject to the Portal Gun's zero-point energy field (which may be because the portal gun is equipped with a weaker field or because the pellet is more unstable, usually exploding after some seconds) and will vaporize the player upon contact. One of these pellets in the final level is strangely greener, and never explodes, causing an extreme game hazard.

OSIPR-fired Energy Orbs can be deflected by a blast made with the Gravity Gun. After it becomes supercharged in the Citadel, the Gravity Gun also becomes able to grab them. Doing this will earn the "Think Fast!" achievement in the XBOX 360 version of The Orange Box.

Aperture Science High Energy Pellet
The Aperture Science High Energy Pellet is an energy ball used in the Aperture Science Enrichment Center's Test Chambers. The equivalent of the Combine's Energy Orb, it kills the player in a single hit. It is introduced in Test Chamber 06. The only difference with the Combine version is a green variant that never explodes.

Deployed by its launcher, the test will often require that it be put in its receiver for the player to proceed further.

While they are very similar, it is unknown if the ASHEP has any relation to the Combine Energy Orb.

List of appearances

 * ''Half-Life 2
 * Half-Life 2: Deathmatch
 * Half-Life 2: Lost Coast
 * Half-Life 2: Episode One
 * Portal
 * Half-Life 2: Episode Two