The leader of a small mining colony that has long been forced to hand its deuterium over to Klingon raiders.
Tessic leads a colony of seventy-six miners on a world rich in deuterium. In Marauders he is reluctant to trade with Archer because his stocks are reserved for someone else, and the crew soon learns that Klingon raiders arrive regularly to take the fuel, leaving the colonists poor and short of medical supplies.
At first Tessic tells Archer to take his deuterium and go, fearing reprisals. Archer persuades him to resist, and with training and a plan from the Enterprise crew the colonists drive the Klingons away.