Chronolock

A chronolock was a tattoo-like force controlled by Mayor Me and the Quantum Shade.

A chronolock appeared on the neck of those judged guilty of crimes in Me's trap street, counting down the minutes until their death. When Rigsy apparently murdered Anah, a chronolock appeared on his neck, counting down from 537 minutes.

When Rigsy arrived in the trap street with the Doctor and Clara Oswald, they witnessed a man who had stolen medical supplies to save his wife get killed by the Quantum Shade when the chronolock expired.

Later, Clara took Rigsy's chronolock to protect him. It later led to her demise, as she was killed by the Quantum Shade. (TV: Face the Raven)