Wyndham catacombs in Elden Ring

Go into the catacombs and turn right from the locked door. Climb down the lift and go through the room with the falling blades. You will find yourself in the sewers. Kill all the enemies and in the place where the knight stood, look for a niche with a ladder. Climb up and you will see a passage ahead that requires sword keys. Activate the lifting plate, which can push you against the spiked ceiling. Jump off it yourself and go down under the platform.

After defeating the enemies, pull the lever on the grate on the left. Go back to the lifting plate with the spikes on the ceiling. Go to the other side, into the room where the knight is standing. He guards the statue with a lever. After activating the lever, you can go back and go into the room with the boss. You will have to fight with the Cerberus of the Erd Tree. For victory, you will receive a Harvester's Bell Orb (1).