2) Euron Greyjoy
Entering late in the series, in season six, it might seem like Euron Greyjoy is just another of Westeros’ wannabe kings, a dangerously psychotic leader in the vein of Ramsay. There has to be a reason why Euron would enter so late in the game, however, killing his brother Balon, taking the Iron Islands and promising to build a great fleet that will conquer Westeros. Clues can be found in the books as to how serious this Euron guy is.
In George R.R. Martin’s novels, Euron is not just some crazy, but a cunning, ruthless man who it’s prophesied poses a very real danger to Daenerys. He also has a dragon horn to bend dragons to his will – something which Asbaek teased would become a feature of the character on the show. We barely know the TV version of this character, but already there are clues to suggest he could be a real threat to those looking to claim the Iron Throne for themselves.