Master of Spiders
The Master of Spiders was the supposed ruler of the spiders on an unknown swamp planet.
Biography
The Master of Spiders sought to keep in order his empire of spiders on the unknown planet which he resided on.
When the Second Doctor with John and Gillian arrived on the planet, the Master was spying on them from his giant mechanical spider. He then released his spiders which pursued the Doctor and his grandchildren into a cave intially sealing them in there for eternity with the other spiders in there.
However the Doctor using his recorder stopped the spiders from reaching them which the Master instead released a net on them and pulled them up. He then sent his spiders using a device to control them onto the Doctor and his grandchildren but the Doctor used his recorder again to interfere with the signals the Master was using which then instead the spider attacked the Master.
The Master however quickly fled into his mechanical spider with the Doctor and his grandchildren getting out of the net. The Master about to attack them, the Doctor quickly fired his newly built ray gun at the mechanical spider destroying it and presumably killing the Master inside. (TVC: Master of Spiders)