Promellian

Promellians were an extinct humanoid species, native to the Alpha Quadrant. At their height, the Promellians were warp-capable and technologically advanced.

A key moment in Promellian history was their first contact with the Menthar species. A Promellian ship unknowingly intruded into a star system considered sacred by the Menthar, and came under attack by Menthar forces. The Promellian ship was destroyed, though not before destroying two of its attackers. Both sides declared war soon afterwards. 

The war between the Promellians and the Menthar would result in the mutual extinction of both races. The final battle was fought in the remains of the planet Orelious IX, in the late 14th century.