Doctor Hess

Doctor Hess is a British Men of Letters elder and one of the two main antagonists (along with Lucifer) in Season 12 of the horror series Supernatural.

She is portrayed by Gillian Barber.

Biography
Doctor Hess serves as the Head Mistress for the Kendricks Academy in England,  used to train future Men of Letters . In 1987, Hess called Mick and Timothy into her office and forced one of them to kill the other to ensure that they would follow absolutely. She handed them a knife, and to Timothy's horror, Mick stabbed him with it.

Season 12
In 2017, while acting as a British Men of Letters Elder, Hess informs Mick that they don't have time to convince the American hunters to join them. She orders Mick to "assimilate or eliminate" and arranges her lackey, Renny Rawlings, to keep an eye on Mick.

Mick returns to the headquarters later on to find Doctor Hess with Arthur. Unlike before, Mick openly defies the British Men of Letters' code of conduct and chooses the Winchester way of doing things. His change in alliance convinces Hess that Mick has gone rogue, so she orders Arthur to shoot Mick point-blank.

While standing over Mick's corpse, Hess announces that the Winchesters must be eliminated and their efforts in America are a failure.

Later on, Doctor Hess orders Arthur  to  the Men of Letters bunker so that they may know all that can about Sam and Dean.