Skull Moon

Skull Moon was a moon and the site of a battle in the Last Great Time War. Gastron was among the Time Lord soldiers who fought there under the War Doctor. (TV: Hell Bent)

The humanoid gunship pilot Cass Fermazzi—who would later meet the Eighth Doctor in the final moments before his death and regeneration into the War Doctor, after he came aboard her ship in response to her distress call as it crashed on Karn (TV: The Night of the Doctor)—was present at Skull Moon and "wept at the massacre". (PROSE: The Day of the Doctor)

As recorded by the Testimony, the "Butcher of Skull Moon" was a name for the Doctor. (TV: Twice Upon a Time)

Skull Moon