The Blue Age rhulisti did build the Tower, the Pearl, and some other stuff I’m sure, that can affect or that draw upon what Brown Age scholars would classify as the supernatural, so that’s psionics, the elements, the land’s lifeforce, the Grey and Black.
It didn’t mean they were mindbenders or elemental priests.
They understood light and shadow well enough that the Tower manipulated those, so it must mean a theoretical understanding of the Black. Science.