In Game of Thrones season 7, a new War of the Five Kings is brewing. The realm trends toward chaos, with the North soon to be unified in rebellion under King Jon Snow while Cersei’s grip on the South is tenuous indeed. Daenerys Targaryen will rally the Tyrell and Martell remnants to her. The Night King, meanwhile, is preparing an invasion from outside. But the fifth king, Euron Greyjoy, just has his tiny Iron Islands off to the West. No big deal, right? Think again: Besides the Night King himself, Euron Greyjoy is the greatest threat facing Westeros.

Don’t Underestimate Euron Greyjoy

Euron Greyjoy is a force for chaos. The king of the ironborn won his position by promising a return to the old ways—reaving, pillaging and conquering. And that’s just what he’ll do, especially when his new Iron Fleet is up and running again. With Westeros on the brink of another civil war, the reavers will have many opportunities ahead—as we’ve seen in A Dance with Dragons, where the Ironborn have begun conquering parts of the Reach and are preparing to move in force on Oldtown itself. Taking the second city of the Seven Kingdoms is no mean feat, but the way for Euron is clear. Moreover, both the Westerlands of the Lannisters and the North are relatively weak and undefended, busy on the one hand with wars elsewhere and a freshly won battle in Winterfell.

Once, the Ironborn under Harren the Black ruled all of the riverlands and much of central Westeros as the dominant power on the continent. That all ended with the coming of the Targaryens. Euron is set to recreate their successes, and again, only a Targaryen has a force that can realistically stop him. Daenerys will ultimately have to deal with him with extreme prejudice.

But Euron may have a larger role to play than that of a mere conqueror. As hints in A Dance with Dragons and preview chapters of Winds of Winter suggest, he is closely allied with dark magical forces. In the books, it looks likely that he will take control of one of Daenerys’s dragons using his Dragonbinder horn. The actor who plays Euron has teased this for the show as well. Moreover, Euron Greyjoy may be the man who brings down the Wall, and the greatest human ally of the forces of darkness. He’s going to be big trouble for everyone in Game of Thrones season 7—but if he steals a dragon and takes down the Wall, he may end up competing for the role of show’s biggest villain.