Once you have opened the door, go through it and claim the first Shard of Aetherium. Shooting them in the wrong order will lead to various enemies and traps attacking you. The order you must shoot the Resonators in are: bottom left, bottom right, top left, top right and bottom middle. You can use any bow and arrows that you have with you but if by any chance you don't have one then you can retrieve Katria's bow, the 'Zephyr', from a nearby log. Here you must shoot the Kinetic Resonators in a certain order to unlock the door in front of you. Work your way through the ruins until you reach the Tonal Lock. Take her journal and a copy of The Aetherium Wars if you don't already have it. Once you enter the location, navigate through a few rooms before you come upon Katria's body. If you don't have the book and are going straight there, the quest marker won't be on your map so use the following image to help you (thanks to the Elder Scrolls Wiki): Travel to Arkngthamz and obtain the first Aetherium Shard:ДЄrkngthamz is located in The Reach, South-East of Markarth. Since this is where you will have to travel once you find the book anyway, it is much simpler and quicker to travel there.Дў.

However if you have completed the main story and still don't have the book, by far the most convenient location is off the body of Katria in Arkngthamz.

Understone Keep (Calcelmo's Dwemer Museum).

You may have picked it up from one of the following locations during your playthrough: The Aetherium Wars is a book found only with the Dawnguard expansion. Find and take a copy of The Aetherium Wars: There are a number of steps required to complete it:ДЎ. 'Lost to the Ages' is an extremely long sidequest exclusive to Dawnguard.

Skyrim special edition lost to the ages