Gorgon.

Proceed through the initial empty rooms of the Marble Gallery.

Drop down through red platforms, avoiding spike traps that impale you when exposed on the floor between them. Watch out for Jack O’ Bones and Nova Skeletons.

In the room with the traps, take the path on the right.

Continue forward through rooms with Skeleton duos and impale traps.

After the traps, the door will be to the right of another skeleton.

The next room is empty.

Enter the room outside the clock room. This room contains two Guardians (LV 60 enemies that grant 1500 experience until level 60) and a Blade. It is recommended to skip the Guardian for now unless you wish to level grind.

Enter the clock room. Drop down the opening in the center.

Break the glass in front of the stasis pods to receive all sub-weapons in the game. The knife sub-weapon is still a good choice.

To the far left of the sub-weapon stasis is a Heart Max up, and to the far right is a Life Max up.

Exit this section and use the door on the right to continue in the Marble Gallery.

The room to the right of the clock room mirrors the room before it, featuring two Guardians and a Gurkha instead of a Blade.

Proceed to the next room, which contains Skeletons and a Gorgon. The Gorgon is a slow-moving bull-type enemy that breathes to petrify you. There is a set of skeletons and a Gorgon on the left and right. Avoid its breath by keeping your distance, as it takes several hits to defeat.

Go through the door on the right. You can fly up towards the ceiling to reach another part of the castle, but this is skipped for now.

The room after the Gorgons is quiet, featuring flying skeleton heads that move up and down.