There are 2 locked doors on the western side of the dungeon, which is not related to any quests shown above.
There seems to be the "Gastyr Key" in the game file, it's just a guess, but didn't appear in the actual game, making those two doors totally inaccessible. If my theory isn't correct, and there's an actual way to open these two doors, add another note, please. Choi Seungmin (talk) 12:03, May 13, 2013 (UTC) Anonymous
There is a chest behind one of those doors...
There are two pressure plates in the prison where one Prismere troll is caged (Hard Lock). The pressure plates do not appear to have any purpose. (Actually there are 6 pressure plates. 4 round the centre of the room and 1 in each alcove between the cages. The cell doors open and close as you run over them. This will release the Prismere trolls of which there are 2, not 1)
You can find the Cuirass and the Greaves of Bolgans' Bane Armor Set inside Castle Gastyr.