Following the finale of its recent sixth season, HBO's Game of Thrones now has just thirteen episodes remaining before it finishes for good, breaking from the established pattern of ten episodes per season to instead conclude with seven episodes in 2017 and six in 2018.
Show-runners David Benioff and D.B. Weiss still have a lot to get through by that time, regardless of the fact that they have now superseded George R.R. Martin's source material and are now ending the story on their terms. As a result of this, you'd expect that almost all of the series' remaining runtime will be dedicated to the characters that remain alive after the sixth season's explosive final episode, with little to none spent introducing or developing significant new additions to the cast.
Season six did introduce some new faces, most notably Euron Greyjoy, who should be set to become a major villain going forward despite appearing in only a handful of scenes thus far. Alongside him, unexpected blink-and-you'll-miss-them appearances were made by the likes of his brother Aeron Greyjoy, Wyman Manderly and Brotherhood Without Banners member Lem Lemoncloak, some of whom A Song Of Ice And Fire readers never expected to see given the omission of their book storylines from the screen.
There's still plenty of individuals that remain missing in action, however, some of whom would've been great additions to the series and some of whom would've been superfluous. Over the next few pages, the fifteen most prevalent will be profiled.
Note that Aerys and Rhaegar Targaryen will not be included, as despite not appearing physically in the series, they are established elements of its backstory.