Dominators

Self-proclaimed masters of ten galaxies, the Dominators were aggressive humanoids dedicated to war. They travelled 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 the planet Dulkis, a peaceful planet ignorant of war for generations and unaware that aliens existed.

The Dominators decided to set off nuclear explosions under the surface, obliterating the planet but enabling them to siphon off the radiation to be used as power for their ships. They also planned to take the Dulcians along as a new slave force.

The two Dominators, the pragmatic Rago and his subordinate, the sadistic 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 on their spaceship as it took off from Dulkis, exploding in the atmosphere.