This chapter is a complete guide for The Field of the Fallen quest. Here you can find tips that will help you to finish this quest in the most beneficial way.
During City of The Sun quest, after you speak with Erend in Olin's house, you are asked to find the murderers of his sister. By using Focus in the place where the ambush happened you can get a lot of information. First, you must meet with Erend in the north where his sister was found.
When you arrive at the place pointed by the marker it turns out that Erend is in danger. Eliminate the machines that attack him and then speak with the man. Ask him about everything and then follow him.
There, you find blood stains that you must examine carefully. It turns out that the bodies were brought here after the murder and scatter around where you stay. Activate Focus to locate wagon's tracks and follow them. After a long walk you end up in the ruins that are nearby. You learn quickly that you are discovered. Your goal is to eliminate all enemies.
When you defeat them, machines will attack you. Immediately after that, there are two Ravagers next to you and, as you can easily guess, they won't have even the slightest interest in Erend. Use fire arrows because they can easily turn the tides to your favor. Another good idea is to use shock bombs but the machines are rather fast which makes aiming with a slingshot much harder.
After that, use Focus to investigate the place where the real ambush happened. The most important points are smashed stones, bloodstain, scattered weapons and a wooden mounting presented on the picture above. After examining all of them Aloy is ready to make the simulation of what have happened. Speak with Erend and the quest will be finished.
A new main quest, which is a continuation of the previous one, is added to your journal - Into the Borderlands.