How can I get a Royal Seal?

Hint 1 of 5:

One might assume that you need to ask a king for something used to make a wax
mark.

Hint 2 of 5:

Fortunately, this is not the case.  You need another kind of seal.

Hint 3 of 5:

The Royal Seal is an animal in the corridor in the castle. This fact makes
your life easier.

Hint 4 of 5:

Usually, seals like fish.