Trilenium is a rare transperiodic element in the megasonic series, usually found in crystalline form throughout the galaxy. It was used to power the warp drive systems of Irken starships. Trilenium regulated the matter/antimatter reaction in a ship's warp core because of its ability to be rendered porous to light-element antimatter when exposed to high temperatures and electro-magnetic pressures. It controls the amount of power generated in the reaction chamber, channeling the energy released by mutual annihilation into a stream of electro-plasma.
Trilenium had an atomic number of 200 and was first identified in 2016 on Galathea, one of Neptune's moons.
Scientifically, use of the prefix "tri-" denotes three atoms, suggesting trilenium consists of three atoms of lenium.