How do I break the window?

Hint 1 of 7:

It's not indestructible.

Hint 2 of 7:

It's just extraordinarily strong.

Hint 3 of 7:

There's something special you need to break it.

Hint 4 of 7:

You need to get into the manor house first.

Hint 5 of 7:

If you haven't gotten into the manor yet, don't read further.