'Game of Thrones' Explainer: The Mountain, The Hound, and What the Heck Oberyn Martell Is Up To

With a number of new characters introduced during this season of "Game of Thrones," not to mention returning characters and re-castings, things can get a bit confusing. That's why we here at Yidio will provide you will "Game of Thrones" explainers to help you understand what exactly the heck is going on.

Today, we'll be looking at the latest happenings in King's Landing, which means there will be show spoilers. Don't read ahead if you haven't caught up with this week's episode!

One of this week's biggest moments was when Oberyn Martell, whose motivations thus far have been murky, offered to be Tyrion's champion in his trial by combat. His reason being that his opponent, Gregor "The Mountain" Clegane, is on his hit list anyway.

Here's where you need some background that's explained in the show, but not in full detail: Back when Rhaegar Targaryen, the son of the Mad King Aerys, was still alive, he was married to Oberyn's sister, Elia. However, he fell in love with Lyanna Stark, sister of Ned Stark, and ran away with her. That triggered Robert Baratheon's rebellion, leading to the events of the series.

When the Lannister soldiers sacked King's Landing at the end of the war, Gregor Clegane was on the front lines. According to Oberyn, Tywin Lannister ordered Clegane to kill Elia's children, and Clegane did...and then raped and murdered Elia as well.

Brutal, right? That's why Oberyn not only wants to kill The Mountain, but is also intent on taking revenge on as many Lannisters as he can...though we're thinking he might give Tyrion a break.