IrishThrones is a fansite that's been good at reporting things concerning filming for scenes in Northern Ireland. Most of their tweets are really just location tweets and spotting trucks and trailers and such. Recently, they let out an uncharacteristically huge spoiler that seems too good to be true since this has been about the third time this return has been teased.
**SPOILERS Season 6** CLOSE SOURCES Lady Stoneheart 'WILL' appear and command an army!— Irish Thrones (@IrishThrones) August 29, 2015
They say they have more to reveal but would like some time to confirm with their "sources" since it's supposedly very heavy and out there. Michelle Fairley still hasn't been seen up there though another fansite speculates that D&D could just cast another actress.
They also had a tweet about Jon Snow's parentage but fucked up the name of his mother.
And in random GRRM news, he's being forced by HBO to attend the Emmys according to a fan who livetweeted an event he attended.
at this point I'm not believing it unless she's on set or I see the episode