Tarydium

Tarydium is an alien element or compound usually found in transparent blue, crystalline form. It somehow contains great power and is therefore desired as a power source by all corporations and species such as the Skaarj. It is at least mentioned in most Unreal games, but doesn't play any role in Unreal 2.

The first Unreal game to feature tarydium is Unreal. The tarydium on Na Pali attracts the prison ship Vortex Rikers which gets caught in the gravitational field of the planet and crashes. On the planet Prisoner 849 discovers the Skaarj are mining the planet for tarydium.

Unreal Tournament 3 features Taryd, a planet rich with tarydium ore.

Weapons
Tarydium has been used in the weapons industry in a number of ways.

The Stinger (Unreal and UC2) was originally developed as a mining tool by Liandri, but was discovered to be an effective weapon as well. It functions somewhat similar to a shotgun, and fires either a constant stream or a short burst of tarydium shards. The UC2 variant of the Stinger can also shoot semi-sentient shards that have a limited homing capability. The Stinger inspired the creation of the Stinger Minigun (UT3) which also uses tarydium shards for ammo.

The Bio Rifle is a weapon that features in most Unreal games. For ammo it uses the waste created when refining tarydium, a toxic green slime called GES. The weapon can quickly fire large amounts of smaller blobs, or one big blob of slime which explodes on impact with living creatures, but sticks to most other surfaces for a short while. The GES may or may not float on water. The GES in the UC2 version seems somewhat sentient in that it will follow nearby players by jumping at them. This version can also turn the GES into a "Bio Mist Cloud" which lingers for a longer while. The Skaarj and related Slith species seem to be less affected by some of the effects of the GES.

In UC2 there are only two kinds of ammo, energy and explosive ammo. All weapons classified as energy weapons use tarydium packs to power them, and seem to be able to extract or use to appropriate properties from the tarydium.