Ser Oswell Whent was a knight of House Whent and a sworn brother of the Kingsguard under Aerys II Targaryen. House Whent is also the birth house of Minisa Tully, wife of Hoster Tully and mother of his three children - Catelyn, Lysa, and Edmure.
Ser Oswell is mentioned in the entry of his sworn brother, Lord Commander Gerold Hightower as recorded in The Book of Brothers. The entry mentions the death of Ser Oswell after refusing to bend the knee to the new king, Robert Baratheon.
In the books
In the A Song of Ice and Fire novels, Ser Oswell Whent was a younger brother of Lord Whent, known and remembered for his dark humor. He wore a distinctive helmet emblazoned with a black bat with its wings spread, symbolizing House Whent. Oswell was present at the Tourney at Harrenhal where Jaime Lannister became a Kingsguard. In the books, Ser Oswell was present with Ser Gerold Hightower and Ser Arthur Dayne in the Showdown at the Tower of Joy with Lord Eddard Stark. After Ser Gerold tells Ned they were not at the Battle of the Trident, Ser Oswell declares, "Woe to the Usurper if we had been." He and his two brothers are slain along with the bulk of Ned's force in the ensuing melee, the only survivors being Howland Reed and Ned himself.