The Power of Kroll is the fifth serial of the 16th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 23 December 1978 to 13 January 1979. The serial is set on the third moon of the human colony world Delta Magna. In the serial, a methane catalysing refinery's operations in the swamp disturbs the giant squid Kroll, which grew in size after ingesting the fifth segment of the powerful Key to Time. When Kroll surfaces, it subsequently rampages on the moon.