DARQ: The Crypt DLC Achievements Guide

With the pictures and the explanations contained in this guide, I hope that I will be able to unlock you if you’re stuck. If you have some questions or if you’ve spot any mistake, feel free to add a comment. I will do my best to update this guide.

The first skull is located in the following room. Once you’ve cracked the puzzle, the piece of furniture on the right of the picture will open. Go back with the head rolling on the floor and go into the piece of furniture. You’ll just have to follow the path to get the 1st Quartz skull.

Reach the elevator room with the head and go bellow it. Then move the elevator up by activating the mechanism with Lloyd.
Once the elevator is upstairs, move the head to the left as illustrated by the picture.

Move the elevator back down to clear the space for the head.
With the head, follow the path down to the right and you will reach the second Quartz skull.

For the last Quartz skull, reach the bell room with Lloyd and the head.

Let the head in this room and move down with the elevator. With the head, follow the path down to the right and you will find the last quartz skull.

There is a dedicated guide for this achivement, I recommand you to check it out!
Crypt Runner guide

Thank you @tasselfoot for this video-guide.

The following picture presents the hidden path:

I recommend you to take the bottom left arrow, then the bottom right and finally the top right.

Once you locked the door with the scissors (first puzzle of the game), put the head on the bridge and activate the mechanism.

Cross the bridge (go the the right) and re-activate the mechanism. You should now be able the reach the following room and go behind the button to the little opening on the wall.

Go this way and you will find where the diamond skull is located.

See Quartz Skull Collector and Jeweler achievements.