Restac was a Silurian and one of the commanders in the their military. She was charged with protecting the city beneath Cwmtaff should its automated systems detect a threat. Like her sister Alaya, she wanted to restore her people's dominance on Earth at the expense of humanity.
Restac looked like every other Silurian, except she had red scales on the top of her head and they appeared to be in straight lines ending on the crown of her head. She also had red scales on her cheekbones and around her forehead. Restac also had a scar on her left eye.
Her twin sister Alaya kidnapped people from Earth's surface and locked them up, presumably for experimentation. Restac was determined to start a war to reclaim the Earth from the human race. She was ordered by Malohkeh (who was also a commander in the military, but preferred his laboratory) and Eldane (the leader of the Silurians) to put down her weapon after threatening to execute the Eleventh Doctor, Amy Pond and Nasreen Chaudhry. Instead, she went on a rampage.
Restac threatened the humans and killed Malohkeh. When she learned Ambrose Northover had murdered her sister, Alaya, she began to drive the humans out, but Eldane released a deadly gas, forcing Restac's warriors to retreat to their hibernation chambers. Restac refused to leave and was killed. With her dying breath, she fired a shot at the Doctor, but Rory Williams threw him out the way and was hit himself. He died and was erased by the time field. (TV: Cold Blood)
Restac was very aggressive and preferred to settle things by fighting instead of negotiating. She hated humans, referring to them as apes. She seemed to be a psychopath, and was even willing to kill her own kind, murdering Malokeh without hesitation or remorse. She was an elitist, believing that she, a millitary leader, should be in charge of everything and everyone
Restac was vengeful. She tried to avenge the death of her sister Alaya and tried to shoot the Doctor even though she could have gone into hibernation to protect herself from a deadly gas that killed her.
Restac was devastated that Alaya had been killed. Although she displayed grief at the sight of her dead sister, Restac usually hid her emotions, showing no signs of concern when Alaya was taken hostage. (TV: Cold Blood)