Game Of Thrones: 15 Early Predictions For Season 8
9. Melisandre Returns (With Assistance)
Melisandre didn't have a great deal to do in season 7, apart from being a sort of gate-keeper to Dany and Jon's relationship starting legitimately, but she did leave a tantalising mystery when she left.
Confronted by Varys on the cliffs above Dragonstone and basically threatened to bugger off and never come back, Melisandre said she would be heading to Volantis, and would then be returning to Westeros where she was aware she would die. So we can probably count on that happening in the final season (hopefully thanks to Davos), but it's the fact that she went to Volantis at all that matters more.
Volantis is one of the most powerful Free Cities, and it's the home of the Temple Of The Lord Of Light, who has a lot of followers there - including those trained to be warriors in his service. If Melisandre is going there, she's going to preach about Jon Snow (who she legitimately believes is the chosen one), and there's a distinct possibility that she could arrive back in Westeros with an army of R'hllor's devout followers in tow.