Fatality Index
From Tardis Wiki, the free Doctor Who reference
File:Missy's Execution Extremis Doctor Who BBC The Fatality Index was used by a species from a Extremis that regulated how that species carried out executions.
Missy was sentenced to death by this species and, in accordance with the Fatality Index, the Twelfth Doctor was chosen to carry out the sentence. (TV: Extremis)