Chronolock

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

History
Whenever a crime was committed in the trap street, a chronolock appeared on the rule-breaker's neck, 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 bread 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)