Ozymandias

When showing the destroyed Citadel to the Thirteenth Doctor, gloated, "Look upon my work, Doctor, and despair." (TV: The Timeless Children).

Behind the scenes
Though not stated in the episode, the Master references "Ozymandias", a sonnet by Percy Shelley, which contains the lines "And on the pedestal these words appear: / 'My name is Ozymandias, king of kings: / Look on my works, ye Mighty, and despair!'"