The “King of the Tunnel” side quests will become available after you defeat Tachy, the Alpha Nayteba, and return from the Matrix 11 location in Stellar Blade. Once you complete the Tachy quest, speak to Cedric, the rude Sentinel in Xion, who is standing near the vending machine close to the Sister’s Junk store.
Cedric will ask EVE to navigate the abandoned Hypertube in the Great Desert to retrieve a lost fusion cell. He seems to have an ulterior motive, but completing the mission will yield many upgrade materials for EVE’s equipment and weapons. This guide will show you where to find the Hypertube and the missing Fusion Coil.

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Where to Find the Hypertube in the Great Desert
To travel to the Great Desert area, speak with Adam at Xion. If you’ve accepted the quest from Cedric, make sure to talk to Adam at the safehouse near the ship. You’ll need to watch the cutscene before he can take you to the Great Desert. When you land in the Great Desert, you should open your map and mark the King of the Tunnel quest and head southwest toward the end of the large metallic tube sticking out of the ground.
There are a lot of dangerous enemies hanging around near the Hypertube, like the Lurkers. If you have a rumble feature active on your controller, you’ll feel the ground shaking before they strike. When the vibration gets stronger, get ready to dive out of the way.
When you arrive at the tunnel’s opening marked on your map, Adam will confirm it’s the entrance. Get ready to surf down to the bottom of the tunnel while trying to avoid as many explosives as possible.
The Hypertube Cave (Where to Find the Fusion Cell)
At the bottom of the Hypertube slide, EVE will land inside a pool of water. Before diving under the water, leave the pool to investigate the two bodies for XP and a Data Bank entry. Climb the ropes at the end of the cave to open the gate and activate the camp area if you’ve activated the Solar Tower.
Retrieve the Old Fusion Cell
Return to the pool of water and dive under to explore. Behind a stack of boxes, there’s another body for EVE to investigate to gain XP and an entry in the Data Bank. Then, swim to the opposite side of the water to open the chest and get the Old Fusion Cell. At the prompt, select “Return to client now?” to return to Xion and speak to Cedric. After a brief conversation, Adam instructs EVE to use the Fusion Cell on the Fusion Drive located in the corner. Inside, she will find a video memory of Cedric’s wife. Following another brief conversation, EVE will receive the following items: 30 Micro Coils, 60 Micro Motors, and 120 Micro Drives.