I have cleaned out the main Windspear dungeon, apart from two locked areeas. I have explored the 5 areas marked "king strohm's tomb" (the ones mostly full of white ghosts) and progressed from the last one (MD0500) to MD0600. This room has a locked door in the floor, just visible behind a pillar while the area map shows there should be a door to the West. If this is a secret door its a very well kept one as none of my party can detect it

I have re-visited all the available areas in this dungeon (several times) and cannot find either a key or a clue as to what to do next - assistance would be much appreciated.
Less important - the journal I found claimed that white ghosts are only hurt by elemental damage. This I assume to be air, fire or earth elementals. Sure enough, the ones in room MD0200 were quickly killed by (I think) conjoured fire elementals, but those in roome MD0100 and MD0300 were not hurt by any of the three types of conjoured elementals. In the end I had to resort to CTRL Y and I am hoping this hasn't messed anything up.
From the readme it seems quite a bit of work was done in these areas for the latest release - have a couple of errors slipped through, or am I just making a series of mistakes? Thanks in anticipation of an answer