Disturbance Witcher 3: Wild Hunt Quest
Group: Main Quests
Location: Kaer Morhen
You'll get this quest after you speak with Vesemir when you get to Kaer Morhen in the "Ugly Baby" quest.
Vesemir told Geralt that Yennefer had set up her trusty megascope as soon as she arrived at Kaer Morhen, but could not get it to function for the life of her. This news greatly troubled the witcher. If Yennefer was planning to use her megascope, that meant a conversation with other sorceresses was in the works - and that in turn meant scheming, politics and other things Geralt truly could not stand.
Quest stages of Disturbance
1. Find and help Yennefer.
You will find Yennefer on top of the tower in the upper part of the castle. She will ask you for help in finding and eliminating the source of the disturbances that make the megascope not work properly. She will give you a device called potestaquisitor that will help you to find the source of the disturbance.
1.1. (Optional) Return to Yennefer.
If you have rejected Yennefer during "The Last Wish" quest, you will receive additional dialogue options when talking to the sorceress. By choosing: Calm down. > Come on. What's on your mind? > I won't grovel. - you will make her angry as a result of which she will teleport you to a lake north of the castle and you will have to run back to her to continue.
2. Find the source of the magical disturbance using the potestaquisitor.
Go down from the tower to the main chamber, use the device you received from the sorceress, and then locate and examine the crates near where Vesemir and Uma are located.
Vesemir will tell you that there are dimeritium bombs in the crates and then he will decide to move the crates elsewhere himself. When he's done, you can go back to Yenn.
3. Let Yennefer know you removed the source of the disturbance.
When you get back to the top of the tower, the megascope will be up and running. It will allow Yennefer to contact another sorceress and seek her advice on the curse cast on Uma.
As expected, Yennefer did not extend Geralt the warmest of greetings. Nevertheless, Geralt, ever the noble and patient soul, helped the sorceress eliminate the source of the magical disturbance. It turned out the culprit was a case of dimeritium bombs Lambert had carelessly placed near the sorceress' room. Tsk, tsk, Lambert.