When I was freeing the Skaal from the Windstone, two Nords died. One of them be Fanari, but at the time did I not think much of it as I was unaware of her importance later on. Trying to figure out how to craft Stalhrim, I realized she was necessary for the quest to do it, otherwise it would be impossible (source being UESP). Is this really true and there is no way of doing the quest or learning how to craft Stalhrim? If so, this, this is truly a sad day.

If you're on PC, you can try resurrecting Fanari; her refID is xx018FCF.

prid xx018FCF

moveto 14

resurrect 1

Otherwise, you might try talking to Deor anyway, and see what happens.

I can't seem to find Deor either, and I saw him leave the Windstone alive. I went into his house and he isn't there either.