Osmund Kettleblack

Osmund Kettleblack is a background character in the fifth season. He is played by an unidentified extra and first appears in "Sons of the Harpy". Ser Osmund is a knight and a member of the Kingsguard, defending King Tommen Baratheon.

Season 5
Five members of the Kingsguard escort King Tommen Baratheon to the steps before the Great Sept of Baelor so the king can meet with the High Sparrow. Members of the Faith Militant block them.

In the books
In the A Song of Ice and Fire novels, Osmund Kettleblack is one of three brothers, sons of a grizzled man-at-arms called Oswell 'Kettleblack', who enter the service of Queen Cersei during A Clash of Kings. Like his brothers, he's a mercenary and boasts of having served in the Disputed Lands and the Stepstones with the Gallant Men - a sellsword company - fighting for Lys and then Tyrosh. He claims of having been knighted in the battlefield by the, conveniently for him, now-dead Ser Robert Stone.

Ser Osmund is named to the Kingsguard after Ser Boros Blount is dismissed on grounds of cowardice for giving up Prince Tommen to agents of Tyrion Lannister to save his own life. Following the Battle of the Blackwater, Ser Boros is reinstated after the death of Ser Mandon Moore and the desertion of Sandor Clegane. Unlike the case of the show, in the novels the roster of the Kingsguard is quickly completed.