Capstone
From Tardis Wiki, the free Doctor Who reference
A capstone was the stone placed at the top of a pyramid.
A segment of the Key to Time was disguised as the capstone of a Martian pyramid. (AUDIO: The Judgement of Isskar)
On Terra Nova, Peri Brown, who had mutated into a half-human, half-bird hybrid, flew to the peak of a pyramid and landed just below the capstone. (PROSE: State of Change)
