Spoilers (as requested)
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I think you are still in the rapax rift. Not yet into the castle itself. This is a different area (requires loading) and has to be reached via the Rapax courtyard.
It has been a long time since i last visited the rapax rift so i got some info from:
www.volberding.com/Wizardry8/Wiz8Mountain-RapaxWalk.htm
A very precise walkthrough. Do not go there if you want to find anything out for yourself!
Upon entering the rapax rift you can turn left or right. Left leads to rafe. Right leads the following (copied from volberdings site):
Go up the steep path to the lava cells - you can click on the levers to lower the grates but you'll need to find some more levers to open the doors to the cells (and get the items stashed inside). Continue on, cross the suspended bridge, and enter the building. The rooms along the corridor contain some nice items and monsters; you should open every door and gain the Sanctum key and the Flamequencher Wand. At the far end of the building are the levers controlling the cell doors - click on them, return across the bridge to the cells, and loot them. Once again cross the bridge back to the building entrance and take the very steep path down to ground level.
Go west and enter the tunnel. Click on the support post in the tunnel to create a partial cave-in which will allow you to cross the lava-filled, narrow tunnel to the right (north). Check out the rooms along your way but your goal is the teleporters at the far end of the corridors. Step into the north teleporter to enter a new area of the Rift.
This should help you quite a bit in the rift.