Not much is known about the Mehtak just yet. Ahska has mentioned them several times as warlike and only concerned with their own goals. They have surrounded the planet of Etimon with satellite outposts, all in an attempt to eventually take over the planet and its great wealth of energy. They are buying Federation technology from the Ferengi and Cardassians.
The Mehtak's skin is constantly regrowing, causing the outer layers to slough off. These layers are high in energy, and the Mehtak use it for sustenance in times of battle.