How can I get inside?

Hint 1 of 6:

Have you been to Quite an Undertaking?

Hint 2 of 6:

Did you see the paintings on the wall.

Hint 3 of 6:

Grey-clad regailia.

Hint 4 of 6:

Have you found anything that might help?

Hint 5 of 6:

The Cloak, it's grey lined.

Hint 6 of 6:

Flip it.