Skarr

Skarr was a Sontaran commander who infiltrated Christmas during the Siege of Trenzalore with a fellow Sontaran from the same clone batch as he. The two Sontarans got into the town undetected having concealed their vehicle with an invisibility cloak. The cloak was unmasked by the Eleventh Doctor's sonic screwdriver. The two Sontarans were destroyed by the Papal Mainframe soon after the detection. Apologising for their death, the Church of the Papal Mainframe notified a relevant afterlife. (TV: The Time of the Doctor)