Missing-In-Action on "Game of Thrones"?

What ever happened to ... on "Games of Thrones"? These characters mostly were introduced in the early seasons of GoT, but haven't been seen or heard from in some time. Odd, considering GoT's impeccable reputation for juggling hundreds of story lines and efficiency in wrapping up loose ends.

Which "Game of Thrones" missing-in-action character* would you most like to see again? * GoT Top250 screen time, multi-episode character and M.I.A. 10 plus episodes

SPOILER ALERT: Intended for viewers current through the Summer 2017 season as poll reveals characters who have gone missing from the Game of Thrones (2011) story line through Summer 2017. (M.I.A. as of 27 August 2017)

Discuss the topic or Take other GoT polls.