Rhaegar Targaryen laid dead on the banks of the Trident – his Royal Army shattered and in retreat. The days of the Dragon Kings were clearly numbered. Until that moment, it would have been foolish to commit Casterly Rock to either the crown or the rebellion. What would our family have to gain in supporting a raving madman, or in entering a crusade to put Robert Baratheon on the Iron Throne.
But chaos benefits no one. It was time for House Lannister to do what it could to ensure a return of peace and prosperity to the land. I, Tywin Lannister, brought 10,000 Lannister troops to the gates of King's Landing in order to bring the bloodshed to a quick and decisive conclusion. King Aerys had been sending Ravens for months, begging for my support to end the uprising. In a way, his pleas had been answered. As I had suspected, Aerys opened the city gates and welcomed my men. Our plan was clear – crush Aerys’ remaining bannermen and remove the remnants of the royal family as quickly and efficiently as possible. Any alternative meant years of further war and a fragmented Seven Kingdoms. Our means were bloody, but the results speak for themselves.
As for Aerys, it is true he met his fate at the hands of my son Aerys have kept Jamie close during the rebellion, thinking himself clever in keeping my son as a hostage should I decide to pledge support to the rebel cause. This proved to be his greatest mistake. For when the time came, Jamie did his duty as a Lannister and drove his sword into the Mad King’s back. With that, Robert Baratheon's crown was secured.
The new king recognized our role in his ascension to the throne just as he recognized how useful the might and riches of Casterly Rock would be if he wanted to keep it. To that end, I offered my daughter Cersei as his queen. Had Aerys not spurned this same offer years earlier, perhaps things would have worked out differently. With Robert and Cersei crowned as king and queen of the Seven Kingdoms, it was a new day. The dragon was vanquished and the Seven Kingdoms were thereafter belong to the stag and the lion.