In this part of the Lost to the Ages achievement guide we will solve the tonal lock puzzle. We will first explain how to solve the door puzzle, but if you are not interested in the explanation and just want to see the solution, just scroll to the end of the guide.

Also note: At this point of the quest, you should have gotten the unique bow: Zephyr. If not, see the previous part of the Lost to the Ages guide here: How to get Zephyr Unique Bow

Katria's Journal Clues
Katria tells you about the Tonal Lock. She points to the Kinetic Resonators up there. Strike them at the right order and the doors should open. But if you hit them in the wrong order, you will be attacked by Dwarven Automatons.

This completes "Reach the summit of Arkngthamz" and gives you the next objective, "Solve the Tonal Lock".

Ask Katria for advice. She tells you that you can pick up where she held off. Her notes should still be in her journal.

Opening the journal and turning some pages, you see:

Katrial's Journal Door Puzzle Clues Lost to the Ages

As you can see, there are five resonators. The bottom left resonator is marked as "1" and the bottom right resonator is marked as "2". The bottom middle one has "3" crossed off, meaning it is not the third one.

Loot the body of an adventurer laying nearby, and you find a Scrap of Paper with another clue:

Paper Scrap Clue in Lost to the Ages

This tells you that the third resonator to shoot is the top left one.

This leaves the fourth and the fifth which can be found by trial and error.

Arkngthamz Tonal Lock Puzzle Solution - Resonator Order
Shoot the resonators in the following order. Use either your bow, or a magic spell:

1) Shoot the BOTTOM LEFT resonator
2) Shoot the BOTTOM RIGHT resonator
3) Shoot the TOP LEFT resonator
4) Shoot the TOP RIGHT resonator
5) Shoot the BOTTOM CENTER resonator

See screenshot below for the Lost to the Ages Arkngthamz Tonal Lock Door Puzzle code:

Tonal Lock Door Solution Lost to the Ages

That is the combination. The doors unlock. Next, you will have to find the location of all Aetherium Shards