Maradnias civil war
From Tardis Wiki, the free Doctor Who reference
The Maradnias civil war was a civil war fought between the inhabitants of the planet Maradnias. The Sixth Doctor unintentionally exarcerbated the war, resulting in the death of billions. After helping restore the Lux Aeterna, Sadok and Lillith altered events so the Doctor's visit there never happened, undoing the war. (PROSE: The Quantum Archangel)