| there might still be a way
perhaps using the console command which kills everything might open the door? ...or give yourself the scroll? (I never use the console).
I can't remember if you can see him at that point.
I would expect that once he is dead, all doors unlock, which would let you into his lab.
alternatively - might it be possible to do something ranged or area? is it possible to gate in something into his lab?
usually spells do not pass doors, but I am not certain that rule is sacrosanct.
I reckon somebody can solve your problem so that you can continue - I hate it when I get to a game stopping moment.
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"All the world's a stage and all the men and women merely players"
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