<p>The Power of Kroll is the fifth serial of the 16th season in the British science fiction television series Doctor Who, which was first broadcast in four weekly parts from 23 December 1978 to 13 January 1979. It is the fifth story in the Key to Time story arc.
The Fourth Doctor and Romana have arrived on the third moon of Delta Magna, searching for the penultimate segment of The Key to Time, finding themselves caught in the middle of a dispute between the crew of a Methane Refinery and the natives (known as 'Swampies'). The Swampies claim the crew have disturbed the waters, and will incur the wrath of Kroll. It turns out Kroll is a giant squid which surfaces every few centuries. Once of normal size, it ingested the fifth segment of the Key to Time and began to grow and became a god-like figure to the Swampies and their descendants.
After Kroll awakens and begins to attack Swampies and the Refinery indiscriminately, The Doctor uses the tracer to eliminate Kroll and retrieve the segment of the key and saves the day (but unfortunately not the universe on this occasion). Both he and Romana go back to the TARDIS and set off on their next adventure.

When script editor Anthony Read asked</p>