The Deathtouched Catacombs is found in Stormhill,  Limgrave. It can be reached by heading west from Saintsbridge.

At the entrance of the catacombs, you will find a tormented spirit. Open the wooden door, and enter. There is a Site of Grace immediately after. Head down and turn to the left, prepare to fight some Skeletons. Some are melee combatants, while others are ranged ones. Remember that skeletons need to be “killed again” once they are down to be put to rest, if not, they will keep returning to life. You will find 2 Grave Glovewort (1) in the first big room.

Keep moving further down, there are more skeletons in the next room. Beware of the Ranged ones that are on the platform as you turn around., get to safety quickly. There is a Grave Glovewort (1) to the right side of the room.

There is a body against a wall that contains Bloodrose in the next room. Also in that room, you will find a statue with a lever, activate it. Retrace your steps, and as you reach the stairs when you fought the first skeletons. Drop down and enter a narrow corridor, now open. More skeletons await, as well as Grave Violet and Grave Glovewort (1). Kill them and take the left exit, you will reach the elevated platform from where the ranged skeletons were shooting you previously. Deal with them. At the end of the platform you will find another Grave Glovewort (1) and a Uchigatana on a hanging body.

Get back to the beginning of the Catacombs, to the room after the Site of Grace. You will notice that the big door is now open. Enter to fight the Black Knife Assassin. Once you have dealt with her, you will obtain an Assassin's Crimson Dagger and the dungeon will be completed. Before leaving, don't forget to loot the chest to obtain a Deathroot.