Klikbrain was a robot.
It was built by Vol Mercurius as an intellectual companion while he lived alone on the planet Dispater. The two played parachess. Abslom Daak went to Dispater to recruit Mercurius to fight the Daleks. They were invading the planet when Daak arrived, which helped convince Mercurius to depart on the Kill-Wagon. He did not take Klikbrain with him, turning it off before he left. (COMIC: Star Tigers, Nemesis of the Daleks)