Tessic's species was a humanoid race. Members of that race had three protruded ridges on the forehead from which some strands of hair was grown. These strands seem to be shorter or weaker on older males with balding hairline.
In 2152, they operated a ramshackle deuterium mining colony on an isolated planet under the administration of Tessic. When the Enterprise visited the miners to trade for deuterium in that year, they found it under duress from Klingon raiders. Since the miners were poorly trained or equipped to defend their quarry, the Klingon Korok had been extorting their resources for some five years with threats of violence. Enterprise Captain Jonathan Archer offered Tessic aid to teach the colonists to defend themselves so that they could win their freedom from the bullying Klingons. They moved mobile structures to expose the volatile plasma pumps with a view to trapping the Klingons there. They also helped train the colonists with firearms and taught them to combat the Klingon bat'leth. When the Klingons returned they were drawn into the trap and finally forced to abandon their quarry. (ENT: "Marauders")