Bloodborne: The Old Hunters is full of fancy new weapons for you to use, and one of the weapons you can find fairly early on in the expansion is the Amygdalan Arm. From the first Hunter’s Nightmare lamp, head right and past the NPC until you get to the bridge standing over the sewer of blood. Instead of following the sewer down to the area with the large foe with the cannon (this path takes you to Ludwig), you want to head left instead.
It should be fairly easy to get past the blood-spewing ladies as long as you keep sprinting. Keep left while sprinting down the path so you can navigate the fallen carriages easily. Once you get past the last carriage, you’ll be out of the ladies’ reach. Continue following the path until it takes you into a cave. Be careful, as you’ll encounter a hunter with a large gatling gun that does a ridiculous amount of damage. Past the hunter, you’ll find a slope that leads downwards and further into the cave.
Unless you’re confident enough to take on all the enemies in the lower area of the cave, I suggest running in and grabbing all the items as fast as you can before dodge rolling your way out of there. The lower area is full of aggressive man-beasts and a non-poisonous version of the much dreaded Blood-Starved Beast itself. The lower area isn’t too big, and you’ll find the Amygdalan Arm lying in the furthest corner of the cave.
“The arm of a small Amygdala Great One. Strictly speaking, the Amygdalan Arm is no trick weapon of any sort, but certain madmen wield them like clubs. Starts as a large, tough blunt weapon formed of bone, but when extended, the hand quivers as if it were still alive.”
