For three years we've been watching him set the pieces up on the board, and with the opening scene of this season, Game of Thrones is making it clear: get ready for the age of Tywin Lannister. As the episode begins, we see him triumphantly preside over the melting down of Ned Stark's giant ancestral sword and toss a direwolf into the fire, the ominous Lannister score bleeding into the booming opening theme. With grandson Joffrey on the throne, his children by his side (and under this thumb), and his greatest threats crushed by his armies, Tywin should finally have it made.
The rest of the episode serves to remind us that for all of Tywin's tactical genius, he's built a new empire on a terribly weak foundation and utterly failed to guarantee that his heirs can properly run the kingdom he's leaving them. And the spectacular closing scene of the episode, a brutal tavern brawl where the Hound and Arya take down a cadre of Lannister goons, shows us what a miserable heap Westeros has become in the wake of civil war. Tywin's ruthlessness has granted him the power he wants, but it's at the cost of pretty much everything else.
It's all crumbling right from the first scene after the credits, where Tywin presents his son and heir Jaime with a beautiful Valyrian steel sword and tells him to go be lord of Casterly Rock, the Lannister homestead. Jaime immediately shuts it down. Has that happened to Tywin before? People usually tend to do what he wants, but what can he threaten his own son with? The only thing he can deny Jaime is his inheritance, Casterly Rock, and that's one thing Jaime could care less about.