Originally Posted by
Amonra
Interestingly, they are called "Defense Crystal" -or something like that- in The Isle of Thunder. Their purpose seems to be pureley defensive, they can be assumed to be some sort of magic storage with defense capabilities.
Previous appearances have described them as blood crystals, but it has never stated if they actually work with blood. It does point out though, to be a technology developed exclusively by blood elves, and the naming might be just for flavour and paying homage to the crystal's red hue. Maybe they require some blood magic to work.
I'm really interested in knowing more about these crystals.