I am in lvl 23 where is room with Cross of Pardon. I have key and open all other rooms with artefacts but this door i cant open. Where is the problem? I was everywhere from 21 - 24 level and not found any item with open this door in lvl 23.

Ok, i got solution. I open door with drag key from inventory and use it on the door :) But if i remember right, first door was open only click on the door and key was used automaticly.

I could be wrong, but I think you need to click&drag that key a few times- keep it handy!