From Cradle to Grave quest guide – Disciples: Liberation

Depending on whether you have visited the Plains of Widows before coming to Grayfall, you may have met your friend Mathieu. He is a traveling bard who happens to now be stuck in a peculiar situation. He has found himself locked inside a cell, and you have to rescue him.

To find Mathieu, you will have to locate the Hall of Souls. To reach this area, head east from where you spawn in Grayfall. You will come to a fork in the road with three banshees. Head south from here. When the road forks again, head east and continue in that direction until you come across the dungeon.

Head into the dungeon and go to the left. You will travel down a hallway filled with jail cells. The last cell on the right is where you will find Mathieu. Talk to him, and he will mention that he is locked in the cell and needs the key to escape. Go back to the entrance of the dungeon and go to the right to find an enemy. Defeat them to obtain the key.

With the key in hand. Head back to Mathieu and unlock his cell. Once his cell is unlocked, he will give you a mysterious key. Now it is your job to figure out what it unlocks. Go out of the dungeon and head north past the banshees until you come across the Tomb of Tuchulkan.

Go inside the tomb and go straight ahead until you reach the room with coffins and two staircases. Head up one of the staircases. If you have not completed the Lost Lullaby quest, a group of undead enemies may surround a book.

Use the key on the wall in the back of the room. The wall will lower and reveal a new room that contains the Tear of Soloniel. Interact with the tear to complete the quest.