Return to the previously saved teleport point. Use the switch you just obtained to interact with the nearby mechanism, which will open the door below.
Jump down through the opened door and descend the stairs. Once down, check behind the staircase for a piece of Dust.
After obtaining the Dust, we can head left to open the iron gate and collect some items.
Open the door to find a chest. Opening it grants "Killing Intent Amber Fragment #1," which is the first piece in Area 2.
