Typically I find it out on my own or google my way to a solution, but I'm stuck with this door in the Black Cove. I've killed the boss pirate, enabled all 13 levers, talked to the girl/father ghost ending up reuniting them, etc, but I've yet to find the key to the Black Omnious Gate where orcs and skeletons fight each other.
Some of the google results suggest that there's a key in the pirate office (with the lever, painting, mounted animal head) next to the stack of books, but with at least 6 (8 buffed) perception, I've not been able to see it. I've spent hours walking around this place searching for hidden stuff, blasting any barrels, etc.
I found one hidden switch behind the painting in the pirate office, and one in the trap house (on the floor, not the one to disable the traps).
Could it be bugged?
Yes. In the office (after the source abomination) check out the corner on the right after you go through the door, and the painting on the wall to the right of the table.
The lever in the corner moves the paining, revealing a switch which in turn reveals a hatch in the corner near the harbour door.
I wonder how many other hidden places I never noticed. Thanks for the tip!