Self-proclaimed masters of ten galaxies, the Dominators were humanoids dedicated to war. They traveled from planet to planet, searching for slaves as well as energy to power their fleets. They had with them lethal robots called Quarks, which could stun or kill on command. The Dominators arrived on he planet Dulkis, a peaceful planet that was unaware that aliens existed. The Dominators decided to set off nuclear explosions under the surface, which would enable them to use the radiation to power their ships. They also planned to take the Dulcians along as a new slave force. The to Dominators, Rago and Toba, argued amongst themselves regarding their duties and methods. However, both were killed, along with the Quarks, when the Doctor placed their atomic device back in their ship as it took of from Dulkis, exploding in the atmosphere.