You may be looking for the short story.

The Nameless City was the home of the Archons. The Second Doctor and Jamie McCrimmon were taken to the city when the TARDIS was hijacked by the Necronomicon, in an attempt by the Archons on a preemptive strike against the Time Lords. The city was made out of black glass, and was built over a pool of gold, surrounded by canals of mercury and Zeiton-7. (PROSE: The Nameless City)

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