This guide shows the complete walkthrough of Black Knife Catacombs, which is in Liurnia as shown in the pictures below. In this Dungeon, you will find a secret boss in addition to the main boss.
After entering the black Knife Catacomb, go down the stairs. Here you will see a closed door with a summoning pool next to it. The main boss of the dungeon is behind this door.
Go further down the stairs and you will see a mist wall on the left side. Use the Stonesword key to clear the path. Inside, you will find Rosus’ Axe.
Continue ahead in the path and eventually, you will reach a room where you will see three large blades moving up and down. If you look above on the left side, you will see a platform. You will have to use the moving blades to reach the platform on top. When the moving blade goes down inside the ground, stand on top of it as shown in the pictures below. The moving blade will carry you to the top. When the blade has reached the top, jump to the platform as shown in the pictures below.
Black Knife Assassin Secret Boss
Continue in the path until you reach the last room. Hit the wall in front as you enter the room. Hitting the wall will make it disappear and reveal an orange mist wall as shown in the pictures below. Here you will find the Black Knife Assassin Secret Boss. Defeat him to get Assassin’s Cerulean dagger & Black Knifeprint.
Open The Main Boss Door
Come out from the secret room and jump down the hole on the left side as shown below.
Pull the lever in front of the statue as shown in the picture below. This will open the door leading to the main boss of the area.
Now pull another lever in this room to open the iron gate as shown below.
Go through the iron gate. Here you will find monster crabs. There is nothing much to collect in this room, except a Rune Arc that you will find on a corpse. So, if you want to skip the fight, then sprint ahead and climb up the ladder as shown in the picture below.
Trace your way back to the start of the catacomb. Now you will see that the boss’s door is open.
Cemetery Shade Boss
Go through the door to fight Cemetery Shade Boss. On defeating him, you will get Twinsage Sorcerer Ashes. Open the chest inside the boss room to get a Deathroot.