How do I get the orb from the cellar?

Hint 1 of 5:

If you could only get past the portcullis.

Hint 2 of 5:

Or the slab.

Hint 3 of 5:

Or the drain. Which is it?

Hint 4 of 5:

It's none of these. The actual solution seems obscure, frankly.

Hint 5 of 5:

Get the orb, then drop something else. If it goes down the drain, get it
later in the sewer.