Dreams in the Gaps is a subquest that you can unlock after meeting Aru in The Subterranean Trials of Drake and Serpent World Quest. You’ll be tasked to find three Reins of Revival, one of which can be obtained from this subquest.
Follow the quest marker to The Narrows and activate the mechanism during Evernight. If Enkanomiya is set to Whitenight, simply find a nearby mechanism that can change the region’s daylight settings.
Related: How to complete The Trail of Drake and Serpent in Enkanomiya Genshin Impact
The mechanism can only be activated with an Attack. Doing so will unlock the gate beside it, allowing you to explore the inside of the secret room.
Once inside, find a hole in the ceiling and climb upward. There’s a nearby Seelie that you can follow to help you navigate the tight space as well.
The item you need is inside the Chest above, but you can’t get past the barrier as long as Enkanomiya is set to Evernight. Interact with the mechanism on the left to change Enkanomiya back to Whitenight, allowing you to get through and open the Chest, which contains the Quest Item Reins of Revival Fragment (The Narrows).
While not part of this subquest, you can also activate the mechanism beside the Chest to open the locked gate to the left, which will, in turn, open up an alternative exit route.
To get another Reins of Revival Fragment, check out our guide on How to complete The Heart of Ouroboros in Enkanomiya Genshin Impact.