In Gandha Hill, located east of Sumeru City, you'll find an Eremite camp with an Energy Extraction Device that can be diffused with the help of Control Keys. Reference the image below to find the exact location of the Challenge. Since the area is swarming with enemy Eremites, make sure to bring a battle-ready team.
Once you get there, you'll find a mechanism called an Energy Extraction Device. Approach it to begin a Challenge where you must find two Control Keys to deactivate the Device.
How to Look for a way to control the extractor in Genshin Impact
In this part, you need to find the two missing Control Keys in order to shut down the Energy Extraction Device. You can obtain them in any order.
First Control Key location
Head to the hill beside the Energy Extraction Device to find a small crack in the building. Upon entering, you'll be locked in. Defeat the Eremites to open the gate leading to the first Control Key. Approach the Control Key to obtain it and open the gate in front of it.
Second Control Key location
After obtaining the first Control Key, turn left to find another entrance leading to the other side of the building. Enter it and climb the ladder to spot the second Control Key. Approach it to obtain the Key and complete the Challenge objective.
How to guard the extractor until it shuts down in Genshin Impact
After obtaining all two Control Keys, interact with the Energy Extractor Device at the top of the building to begin a battle segment. A circular gauge will appear above it. Your goal is to stand beside the Device until the gauge above it becomes full. If you're too far away or if there are enemy disruptions, the gauge will stop filling up, so make sure to defeat all the enemies that spawn and stand close to the Device afterward. Once the gauge is all filled up, the Energy Extraction Device will turn off, rewarding you with an Exquisite Chest.
Check out our guide on How to complete the Energy Extraction Device Challenge in Vissudha Field in Genshin Impact to solve a similar Challenge in another part of Sumeru.