Gat

 was a Gallifreyan who worked with the Doctor. She worked with the Judoon to capture the Doctor.

When she captured the Doctor, Gat was surprised when she was confronted with the Thirteenth Doctor. She cited the Blinovitch Limitation Effect, terming it an "abomination."

She was horrified when the Doctor told her Gallifrey was gone, presuming she was lying.

She was killed when she tried to shoot the Doctor with a laser rifle as it had been calibrated to shoot the one holding the gun. (TV: Fugitive of the Judoon)

It is unknown whether she did not regenerate because she had run out of regenerations, or because the gun had been calibrated to stop regenerations. Although difficult it is entirely out of the question, since the gun was calibrated by Ruth Clayton or "the doctor" much is unknown about ruth, but as a time lord she, would now how to effectively kill Gat.