Elerium-115

Elerium-115 is a fictional element featured in the X-COM video game series, with similarity to Robert Lazar's conspiracy theories about Ununpentium (Element-115). It is said to contain high amounts of energy. In the first X-COM game it is only acquirable by capturing intact alien Power Sources (50 units of E-115/Power Source) and cannot be manufactured, thus making it one of the most valuable items in the game. In later games, it is mined on other planets by third-party corporations.

Enemy Unknown
In the first installment of the series, Elerium is first discovered when scavenging intercepted UFOs. It is used by aliens for propulsion and for their special plasma weapons. Elerium is said to give energy by the following way: if it is bombarded with accelerated particles, part of it will transform to antimatter; the matter-antimatter mutual annihilation is the reaction which gives the energy, but the reaction also emits gravity waves and a functioning Elerium-powered reactor also generates its own gravity field, independent from all outside gravitational interference.

Later in the game the player also develops his or her own elerium-powered weapons called the Fusion Ball Launcher (following the example of the alien weapon Blaster Launcher) and the Plasma Cannon (based on reverse-engineered alien plasma-based weaponry technologies). It is depicted in the game as an orange crystalline substance, but incidentally it has the same graphic as that of a Stun Bomb in the Battlescape (purple ball). (Not in the Amiga version. In Amiga version, the graphic is the same as the ufopaedia.)

Terror from the Deep
In X-COM: Terror from the Deep, the second installment of the series, taking place in 2040, the amount of Elerium harvested from the aliens in the first war are long gone. However another element called Zrbite is used by aliens in the second war in a similar way as elerium but seems to be a bit richer in supply. It is part gold, part alien biometal; because of the latter, it cannot be manufactured, since some of its components are unknown to human science.

When the Second Alien War ended, all Zrbite on the world has become inert, since the aliens' molecular control network was the key to unlocking its power. However, it isn't forgotten; in 2054, the Transtellar Corporation unveils the prototype for the Mark I Conversion Drive, an ion propulsion system that generates power through helium-carbon fusion. The key to the success of the design was the use of a reaction containment chamber with a shell composed primarily of inert Zrbite.

Apocalypse
In X-COM: Apocalypse, the third installment of the series, Elerium is used to power all engines and most weapons and can be bought from a corporation known as Solmine, which mines it from Mars. Although it is quite affordable through the game, the supply is limited. Acquiring it can become an issue if the player operates multiple craft with plasma weapons.

Interceptor
In X-COM: Interceptor, the fourth installment in the series but taking place third in the timeline, a synthetic form of Elerium-115 is developed and is considered weapons grade, allowing the deployment of various new weapons systems. During the game prior to this, the use of the element for military purposes other than power generation or propulsion was prohibited due to the limited supplies.

Although research from the first installment says that Elerium is not naturally found inside the Solar System, in October 2061, after several weeks of transmissions, the Mars probes show an indication of what could be a huge stockpile of Elerium-115 several thousand kilometers from Cydonia. Plans are immediately set in motion to send a manned expedition to Mars-the first since the final X-COM cleanup mission in November 2009. The first ship, the Patton, triggers an alien device in the ruins and disappears above Cydonia forming the basis for the unreleased X-COM: Alliance, more ships are sent however and a mining colony established.

The Elerium mined there was enough to partially satisfy Earth's needs and enable humanity to seek new sources further afield, as such Transtellar purchased all rights to interstellar research abandoned when Elerium stockpiles from the first war ran out. In a matter of months, Transtellar finished plans for a prototype hyperdrive, tested successfully in 2065, this allows Elerium mining platforms to be set up in the asteroid belts of other star systems providing the frontier setting of X-COM: Interceptor.