Robert's aforementioned feather makes its own significant appearance in this teaser. When it blows out of Lyanna's hands, it lands on the floor as Jon walks away. There's a bit of irony in the fact that Robert made a vow to kill all the Targaryens (referring to Dany) and the one he should have truly been looking for was under his nose all along. And now, he can't do anything about it. The last time we saw the feather was in season five when Peytr recites the story of the Tourney at Harrenhal to Sansa.