Why you should keep an eye on Euron Greyjoy in 'Game of Thrones' this season

The battle for the crown has been raging for years on Game of Thrones, but never with Euron Greyjoy. The current king of the Iron Islands (it's so hard to keep track!) has recently aligned himself with the Lannisters and turned on his own family -- and he's just getting started.

Let's recap for a moment who Euron even is. He's the younger brother of Balon Greyjoy, and the uncle of Yara and Theon. He killed his brother for the throne, because everyone's doing it! And now he's captured his niece and will hunt down his nephew (if he even thinks Theon is worth the time).

Before we met him in the show's timeline, Balon was a pirate, exiled to the seas after destroying Tywin Lannister's ships during the Greyjoy Rebellion. The story is that he went a little mad at sea; his crew tied him to a mast so he wouldn't jump into the turbulent waters, and when they eventually released him, he had all their tongues cut out.

So yeah, that's the guy on Cersei's side now.

Since he returned to the Iron Islands in Season 6, Euron started causing all sorts of drama. He might be the worst, but you have to begrudgingly respect his focus and energy. He dethroned Balon and took over the Salt Throne faster than you can say "What is dead may never die."

He built a fleet with the suspicious speed of Arya Stark crossing the Narrow Sea, and in this week's "Stormborn" we watched him attack Theon and Yara's ships while swinging an axe with Ramsay-esque mania.

Original image has been replaced. Credit: Mashable

Having someone as remorseless as Euron on her side has obvious advantages for Cersei, but it's still not clear what the axe-wielding Ironborn has to gain from this alliance.

In the books, Euron is explicit about his desire to marry Daenerys in his quest for the throne; in the show, he mentions her in Season 6 but then decides to support the Lannisters. Destroying Dany's ships weakens the Dragon Queen significantly and messes with the entire battle plan she laid out on that table at Dragonstone. Each time she suffers a defeat, she has need for more allies -- even Euron.

So why back Cersei?

As Tyrion tells Daenerys in Season 7, Cersei has maybe three of the seven kingdoms backing her, and the rest in open rebellion. She can't control her people, and everyone who gets close to her ends up dead (including her children). Daenerys has thousands of Unsullied, the Tyrells, Dorne, three dragons, and -- soon -- Jon Snow and the North. She has a legitimate claim to the throne as a Targaryen and it's no accident she's being compared to Aegon the Conqueror.

Euron seeks out allies who need him -- allies with a known weakness. Cersei's vulnerability is what made him choose her, and Daenerys will be back in play the moment she needs more help. If Euron turns on the Lannisters, he could take his massive fleet of ships to Dragonstone and offer up his services to Daenerys and easily take King's Landing by sea.

Over the course of just a few episodes, Game of Thrones may secretly have turned into Game of Euron. Keep an eye on this guy -- he holds more power than anyone suspects, and he's not afraid to use it.