The mother of all bullshit plot twists awaits us!
I had intended to show this off on-camera, but accidentally saved over my old file. Ah well.
If you go south of the docks on Skara Brae, you'll find a locked chest behind a wrecked wooden boat. Normally you would need to begin the game as a Ranger to get the key that unlocks this, but you can still reach its contents thanks to the janky engine. Poke around with the cursor and the X button to find the Blackrock Helmet (this is the only place you can get it, unless I'm very much mistaken) and some Blackrock Gauntlets (if you chose not to buy them in Buccaneer's Den), then just pull them out and equip them.