During the Game of Thrones Season 4 premiere, we heard new character Oberyn Martell (Pedro Pascal) give an account of his sister Elia to Tyrion, but just who was this woman? And what is her importance to the overall storyline?

Get out your notebooks, class, it’s time for a Westeros history lesson!

Note: This article contains information from the A Song of Ice and Fire book series.

Elia Martell was a Princess of Dorne, the southernmost kingdom of the Seven Kingdoms of Westeros. House Martell has their seat at Sunspear and is the ruling house of Dorne (just like how the Starks had their seat at Winterfell and were the ruling house of the North). Elia was the sister of Prince Doran, the current Lord of Sunspear, and Prince Oberyn, whom we met in the season premiere.

When Elia was alive, she was married to Rhaegar Targaryen. Rhaegar was the eldest son of the Mad King Aerys Targaryen, and was the brother of Viserys and Daenerys, but was much older, being of the same generation as Ned Stark and Robert Baratheon. While Targaryens typically wed each other to keep their bloodline pure, there were no Targaryens of age for Rhaegar to marry, so their house was joined with House Martell, and he wed Elia, making her next in line to be queen.

Elia bore Rhaegar two children, Rhaenys and Aegon. During their marriage, Elia and Rhaegar got along but were not in love. Elia was sickly, and Rhaegar was in love with Lyanna Stark, Ned’s sister. Seventeen years prior to the events of Game of Thrones, Rhaegar abducted Lyanna (or she went with him willingly, depending on who you ask) and this event triggered Robert’s Rebellion, since Robert Baratheon was betrothed to Lyanna. The Houses Stark, Baratheon, Arryn, and Tully rose up against House Targaryen, which was supported by House Martell, largely because King Aerys kept Elia and her children in King’s Landing to ensure Martell allegiance.

During the war, Robert killed Rhaegar in battle and Ned Stark found his sister in Dorne, and she died shortly after. King’s Landing was sacked by the Lannisters, who had remained neutral during the war until the winner became apparent. Tywin led his forces to the gates, claiming to come in support of King Aerys, and when Aerys opened the gates the Lannisters sacked the city. Jaime Lannister slew King Aerys, and Tywin, not wanting to leave any Targaryens alive, ordered the murder of Elia and her two small children. The order was carried out by Lannister soldiers Armory Lorch and Gregor “The Mountain” Clegane (the Hound’s brother). Lorch stabbed Rhaenys fifty times, while Gregor smashed baby Aegon’s head against a wall in front of Elia before raping her and ultimately murdering her.

Since this event, House Martell has held an understandable hatred toward House Lannister. And now you know why Oberyn Martell is seeking vengeance for his sister Elia.

Are you Team Oberyn? Let us know in the comments below.