Doctor Who: EVERY NuWho Villain And Monster Ranked Worst To Best

Appears in: Face the Raven.

From the birds in Alfred Hitchcock's classic film of the same name to Ernie the Giant Chicken from Family Guy, we can also add the Quantum Shade, which took the form of a raven, to the list of belligerent birds.

As the Doctor explained to the initially doomed Rigsy:

"Once it's bound to a victim, you could flee across all of time and all of the universe, it would still find you."

Ashildr - in her Mayor Me persona - used the Quantum Shade as the ultimate deterrent to maintain peace in Trap Street: those that committed crimes were marked with a chronolock, a countdown tattooed on the back of the victim's neck.

Clara bravely/stupidly took Rigsy's chronolock, thinking that Ashildr's absolute protection would prevent her from being killed, but her act of supreme selflessness backfired in the most tragic way.