Metreon

Metreons are particles that can take the form of either gas or radiation. Metreon particles react with dark matter, while metreon gas is extrememly volatile and easily weaponized.

In 2153, Captain Jonathan Archer and his science officer T'Pol were able to excite a dark matter nebula using spatial charges that spread metreons throughout the nebula. 

In 2154, the Enterprise used a pocket of metreon gas to reflect the ship's engine signature and create multiple sensor ghosts when entering a nebula controlled by the Korvaalans. 

In 2356, Haakonian scientist Ma'Bor Jetrel created the metreon wave, a devastating weapon that his people deployed against the Talaxian moon Rinax, killing all of its inhabitants. Jetrel and others exposed to the metreons developed a fatal disorder known as metremia. 

In 2371, Jetrel encountered the USS Voyager and attempted to use its transporter to reintegrate the remains of the victims of Rinax, who had been held in a state of animate suspension. Unfortunately, the remains were too fragmented for this method to work. 

In 2375, the USS Enterprise (NCC-1701-E) was able to escape from the Son'a in the Briar Patch by using the ship's ramscoops to collect metreon gas and then deploy it in front of the Son'a warships. When one of the ships fired on Enterprise, the metreon gas ignited, destroying one ship and damaging the other. 

Later that year, Voyager became trapped in a cloud of metreon gas. The ship was then attacked by Hazari, forcing Captain Kathryn Janeway to ignite the cloud of gas using the ship's phasers in order to escape. 

In 2402, Toral, son of Duras used a metreon wave to destroy Federation Outpost 15. He then threatened to destroy Cygnus III the same way if the Ambassador Alexander Rozhenko did not commit ritual suicide. Rozhenko did commit suicide and Starfleet was able to apprehend Toral and his group of terrorists before they used the weapon again. (SS TNG (Staying the Course))