We are now back inside the Slaughter Tower. There's a bag on the left that can be shot down with a bow and arrow, then go through the pipe to collect the resources on the right.
There's a ladder next to the resources that you can climb down. Below is an item we just knocked down earlier.
Continue forward, defeat the enemies ahead, and pick up the purple item on the left.
After obtaining this purple item, turn around. There's a path leading down on the right.
You can also go down from here; there's a self-destructing fat enemy ahead.
After the self-destructing fat enemy explodes, open the chest ahead. You'll obtain the weapon soul-forging material "Sharp Darkgold".
