Oblivion - Main Quest 3 - Find the Heir

Once you arrive at Kvatch, you will find the city is in ruins. There is a camp of refugees at the bottom of the hill, and the city at the top. Hirtel will greet you in haste as he is running away, explaining that the city was overrun by daedra the night before, and that a few guards are fighting back the creatures pouring forth from an Oblivion Gate blocking the entrance to the city. Venture to the top of the hill and you will find a few soldiers defending the city, notably Savlian Matius. If you go around the Oblivion gate and into the Chapel of Akatosh inside the city, you will find Brother Martin and more survivors. Martin will refuse to leave with you, saying that he does not want to leave the civilians behind to fend for themselves. Speak to Matius again, and tell him that you want to help. He will give you your next quest, Breaking the Siege of Kvatch, which will require that you venture into Oblivion itself and find a way to destroy the gate to save Martin and the other survivors.