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I am trying to remember a title for a very large older book that featured among other things a dying race of very tall, graceful people living on a desert planet. They live in a spire and have a matriarchal society.
I remember them dressing all in black and using swords.
Other points I remember:
They leave the planet at some point (I think).
They find ruins of their race that are very, very old.
Main character also seemed to be a slightly rebellious young man.
I'll try and update if I remember anything else.