My birthday is this time of year and years ago I had a dream, in May, about a birthday party for me, that was attended only by dead people.

My grandmother was there, who had died about a year before, and everyone there I had known slightly at least and every single one was dead.
We were eating, and talking, and I knew that I was not supposed to break the spell as it were, but I asked my grandmother if I would ever see her again.
This did break the spell and it all ended and vanished.

That is all I can remember.

Birthdays are a time for reevaluating your life, reminiscing about the past and thinking about your plans for the future, so it makes sense that you would dream about dead people (memories from the past).

Having a birthday can also make you think about your own mortality. That could explain why you had this dream.

"Breaking the spell" and not being able to see your grandmother again could represent not being able to go back and relive the past again; not being able to become younger again.

It was spooky to get this dream! For sure.