Netherrack

Netherrack was a part of 'Netherrack Thermocouplings', a component of the TARDIS. (NOTVALID: Doctor Who Minecraft)

Behind the scenes
Netherrack was a block in Minecraft typically found in the Nether, a hell-inspired dimension accessible through an obsidian portal lit with a flint and steel. If lit on fire, it would never stop burning unless put out by something else in the game.

The block was used in various builds in NOTVALID: Doctor Who Minecraft, such as a recreation of the Capitol on Gallifrey, a planet seen in a transmission from Ben, and the ground on which Stampy walked in a behind the scenes section.