Gat

 was a Gallifreyan who worked with the "Fugitive" Doctor. She worked with the Judoon to capture the Doctor following their disappearance, and upon discovering the Doctor's location, she executed Lee Clayton and proceeded to search for 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 later revealed to the other Doctor she was an agent of Gallifrey, working for the Division, and was horrified when the Thirteenth Doctor told her Gallifrey was gone, presuming she was lying.

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

Behind the scenes

 * As of The Timeless Children, it is shown that the Shobogans, the original Gallifreyans, invented the Division, implying that Gat might be Shobogan.