I have found the Rift Key - late in the Rapax Castle, but cannot figure out where to use it?

I think that I have been everywhere, even the cellars, don't recall any doors, that I can't open. So where does this go?

Also found red silk robes (I think) - seem nice, but only sell for 125g, anmy idea what they are for.

And the pickled trynnie - says its other? - what does this do? - how do I use it?

Sorry for the multiple questions, just strange stuff I need answers for - Thanks

Rift key.. remember the place where you made the ceiling collapse? there was a door you couldn't open.. use the rift key on that door.. it's just a 10-second shortcut, you don't NEED to do it..

The pickled trynnie.. give it to ferro, for the armory key.. you can use the armory key if you go back in his shop, take the small lift up, and use they key on the cubbard.. you should get some nifty items.

The red silk robes are a worthless item. They give you no AC bonus and while I don't know for sure because I didn't try them on in 8, in Wiz 7 anything that was "silken" or "oliveskin" or things like that were all cursed items that actually were detrimental to your AC.