Rock Knight.

In the first room of the Underground Caverns, grab the Shiitake mushroom on the far left.

Proceed through the opening above.

Take the path to the right, then return to the left path.

Defeat the Cave Trolls (2-3 hits each) that run at you and shoot projectiles when they stop.

Defeat the Dark Octopus by diagonally swinging with your weapon from higher ground.

After more trolls, break a candle near the ground to find a $2000 bag.

Continue to the end of the path to find a door leading to the ALUCARD SHIELD. Equip it.

To get map coverage (you check the map with the Select button), eliminate all enemies in the water sections first.

Start on the far left or right side of the water section.

Transform into a wolf and swim by holding the dash button (Triangle).

Swim with the wolf hugging the ceiling towards the other side of the room.

If the map shows a white line completing the room's perimeter, you have achieved map coverage for that side. Repeat for the other side.

Go left over the opening to the other side of the Underground Caverns.

Walk through empty hallways until you reach an inverted Waterfall.

Go through the waterfall to find the Osafune katana.

Leave the room and get map coverage of the waterfall area and the other side.

On the opposing side of the waterfall, find Shiitake and Toadstool consumables.

Drop down and enter the room on the bottom right to find a Garnet.

Leave the waterfall room.

In the next room, swim towards the Bat Pentagram item using the wolf form to obtain it, as it pushes you away.

Proceed through the next few rooms where the difficulty increases, encountering Blue Venus Weed and Rock Knight enemies. You will need to spam attacks or use Mist form to escape due to the tight terrain.

After the initial encounter, defeat a single Venus Weed and a single Rock Knight.

Above the Rock Knight is the entrance to the catacombs.