Earlier this morning, HBO released several new character posters in the Hall of Faces motif for the upcoming sixth season of "Game of Thrones." The Martells, Targaryens, Starks, Lannisters and other important families were all represented by patriarchs and matriarchs both living and dead. However, one character was featured and then immediately erased from HBO's Twitter timeline.

Thanks to screenshots from some keen-eyed observers, we know the character poster HBO tried to put back in the bottle was that of Nymeria Sand (Jessica Henwick), who served as one of the Sand Snakes from season five. The image was initially tweeted out by @HBOAsia.

But why would the network want to hide Nymeria? She's not a new character, after all, and it's not as if the fifth season spent a significant amount of time developing her. Though she did play a role in the murder of Princess Myrcella, it's not as if she was the ringleader.

So why all of the secrecy?

Warning: Spoiler Alert for "A Dance With Dragons"

Perhaps HBO is nervous because Nymeria won't even be in Dorne during the upcoming season of "Game of Thrones." In the latter part of "A Dance With Dragons," the fifth book in George R.R. Martin's novel series "A Song of Ice & Fire," Prince Doran sends two of his nieces to King's Landing. Nymeria and Tyene are his chosen delegates, with the latter tasked with getting close to the High Sparrow and the Faith Militant and the former replacing her father Oberyn on the Small Council. This decree is the last time readers see the Sand Snakes (until they presumably show up in "The Winds of Winter").

While the HBO series will take some creative liberties with the planned storylines of Martin's upcoming novels, this is a clear reveal that the show plans to use Nymeria in a fairly crucial capacity this season. Dorne's introduction to the main storyline was not well received by fans last year so this could be a shot at redemption. Who wouldn't want to see Nymeria exact some long overdue revenge on the Lannisters?

We'll find out how exactly Nymeria fits into season six's plot when "Game of Thrones" returns to HBO on Sunday, April 24.

Follow Brandon Katz at @Great_Katzby