First seen in:
Invasion of the Cat-People
The Euterpians, as they were labelled by the Federation, were an advanced humanoid race that naturally encompassed the three dimensions of time, space, and transcendentalism. They were able to use harmonics and ultrasonics to bring things into existence simply by singing, screaming, or humming. This allowed them to kill or control people save for their own as their minds possessed barriers. They were essentially immortal, barring being killed.
Euterpian spaceships were held together by the combined singing and balanced harmony of all onboard. If this balance was upset, the ship would fall apart. A re-con leader and constructionists would be sent to planets from ships to arrange a ring of beacons, similar to thermonuclear devices, which would cut planets in half and release the magnetic energy for the Euterpians to harness.
During the Millennium War, the Euterpians and the Greld used the battle shroud of the Semquess and wielded the Omnethoth, destroying an entire galaxy to destroy a thousand of the Mad Mind’s fleets. (The Quantum Archangel)
Circa 40,000 BC, five Euterpians were stranded on Earth after solar flares destroyed their mothership. They survived and taught the Aborigines their mythology of the dreamtime and the songlines. By 1994, the Euterpian homeworld had been gone for 10,000 years. (Invasion of the Cat-People)
Euterpians were involved in the ancient battle with the Aesirians, alongside the Osirans, the Dæmons, and the Time Lords. (Hacked)