Vaisey, the Sheriff of Nottingham, is the main antagonist of the 2006-2009 TV series Robin Hood and the archenemy of Robin Hood (the series' titular protagonist).
He is portrayed by Keith Allen.
History
Vaisey was made Sheriff of Nottingham by Prince John, taking over from Edward of Knighton, while King Richard fought in the crusades. He was well known among his people for his excessive taxing and intense cruelty towards his people when they stepped out of line.
As the series progressed, it became clear that Vaisey is an exceptionally power-hungry individual, seeking control of England for himself (causing Prince John to order Vaisey's former close friend Guy of Gisborne to kill him in the final series), and in early episodes it was made clear that he is a psychopath, who is willing to use any excuse under the law to kill as many people who oppose him as possible. He is also the leader of the Black Knights cult, within which he had ordered a failed assassination attempt on King Richard's life (to be carried out by Gisborne) during the crusades.
After his alleged death at Gisborne's hands, Vaisey amassed his own army, first using it to take over Nottingham, then presumably the rest of England, but he is stopped by Robin Hood and his merry men (and Gisborne), though not before personally killing Allan-A-Dale.
In the series's final episode, Robin kills Vaisey using his own weapon (Byzantine fire), before dying himself as a result of being stabbed with a poison-tipped knife by Isabella Thornton.