Find the Heir - The Elder Scrolls IV: Oblivion
Your journey takes you to the city of Kvatch where you must search for Martin, Uriel Septim's illegitimate son. Through your conversation with Jauffre, you learned that Martin is serving as a priest in the Chapel of Akatosh.
Kvatch is located far southwest of the Imperial City. If you choose to walk there, set “Find the Heir” as your active quest to have a red quest marker appear on your map and compass. However you decide to get there, once you reach Kvatch, a man named Hirtel will approach and initiate a conversation with you. Hirtel brings grave news; the city of Kvatch is now in ruins. He explains that a swarm of Daedra poured out from an open Oblivion Gate and immediately took to destroying the city.
Up the road you'll find what's left of the people of Kvatch. The townspeople in the small encampment at the foot of the ruined city offer little help in regards to locating Septim's heir. You need to make your way up the hill and enter what is left of the city of Kvatch. A linear path just north of the fire in the middle of the encampment leads right up to the city gates.
The sky shifts to an ominous crimson as you ascend. Once you reach the top, you will find what is left of the Kvatch guard. Savlian Matius will approach, ordering you to turn back. Select “Help” from the dialogue options to offer your assistance. This adds the quest, “Breaking the Siege of Kvatch” to your journal.
The Oblivion Gate outside of the Kvatch.
Proceed to ask Savlian Matius about Martin; he explains that Martin is likely still alive, as he is probably with the group that barricaded themselves inside of the Chapel of Akatosh deeper in the city. Before you can speak to Martin in Kvatch, you must first progress in the “Breaking the Siege of Kvatch” quest.
When you have completed the “Breaking the Siege of Kvatch” quest, speak with Martin and have him follow you to Weynon Priory. If you choose to fast travel to Weynon Priory, Martin will travel there with you. Upon your arrival it becomes evident that trouble is brewing. Eronor, a Dark Elf, will initiate a conversation with you and explain what is going on. He tells you that Prior Maborel has fallen, but Jauffre may still be alive inside the chapel.