Vae Victis comes from an interesting point in Rome's history. In 387 B.C., Brennus attacked and then held Rome for three months. In what could be a Roman ideology, they offered a ransom. Brennus asked for his weight in gold. When the scales were set, it took nearly a thousand pounds of gold to true the scales. Obviously far more than Brennus's weight. When the Romans complained of the obviously rigged scales, Brennus tossed his sword onto the scales and exclaimed "Vae Victis." The Latin term is most commonly translated to "Woe to the vanquished" or also "Woe to the conquered." Basically those who have been conquered had no right or place to complain of their situation. It took even more gold to true the scales again.
Vae Victis is seamlessly integrated into the original game. There is no harsh line of distinction between the two. Whereas this is always nice for the player, with seamless game integration, it can make comparing the two very difficult. The social implications of this expansion are as epic as the game itself. Citizens of this historical macrocosm will actually begin to take on their own paths in their world. At first, I felt like they were doing nothing but fighting with one another. Then I remembered they were supposed to be humans.
In most "God" games, you sit at the top and look down. Your word is final. You are, after all, Caesar. The Senate function in this game does a great job of tapping you on the shoulder and saying, "Hey! Knock it off," or "I don't think so." Your social party will play a huge part in the direction in which you take your empire. You now have to bend the Senate to your will along with the people. Otherwise, you will find laws that have been placed by the Senate that prevent you from getting your way.
Expect to be receiving many orders and challenges from this Senate. They go even further with Tribes and nobles setting their own courts and laws. You will need to rally them to your aid as well. They are not all out to get you. A good Caesar will move the Senate to pass laws and decrees that will allow you to rule your empire. If you cannot balance all of the characters in play with the Senate, courts, and conspirators, you may find yourself with the dagger in your back uttering, "Et tu, Brutus?"