During the main quest “In the Grip of Entropy” in Dragon Age: the Veilguard, you can come across a small puzzle related to door. There is only one crystal next to the only passage., supplying energy to the door. To go further and help Bellara take the elven artifact, you need to find the second crystal.
How to find the second crystal and open the locked gate, you can find out from our guide.
How to supply energy to the door in Dragon Age The Veilguard
During the quest with Bellara, after the battle with the sentry, you will find a closed door. The first crystal will be next to the pedestal. However, the second crystal will not be visible nearby.
How to find the second crystal
Take the first crystal and move it to the small door on the opposite side of the square. Go upstairs and, after destroying the fel pustules, gain access to another ballista.
Interact with it to break the only empty wall opposite. After the wall is destroyed, do not rush to move away from the ballista. Use it to destroy the enemies that burst out from behind the wall.
Go back down and move the first crystal to the pedestal by the main door. Then, follow the resulting passage and immediately turn right. Take the second item and carry it to the door to supply enough energy to power it.
Once the door opens, you will be able to continue your search for the ancient elven artifact in the company of Bellara.