-all credit to Academia Nut for the concept
During the last few hours of the night a thing of shadows was wrought by a single person. It was a construction of alchemy never before seen in this land, it was a star fortress, a great defensive work that had overlapping kill zones in every direction. The only way to get to the gates (well the place where a gate would have been if Rorona had the supplies and energy fr that matter to make it) was via running a gauntlet that would allow the defenders to shoot at the fronts and backs of their enemies. Basalt and granite, diamond and sapphire, steel and stone composed the structure, folded and blended mono-crystalline sheets that formed one solid, contiguous unit.
But those that gaze upon it see not the solidity of the massive structure, for it appears almost deceptively translucent despite the fact that it is opaque from one side to the other, for sheets of clear diamond and dark blue sapphire set on top of mottled black and gold stone create the image of near intangibility. Variances of the chemistry within the gem layers produced sparkling three dimensional dots that shone like stars. It appears as if the very night sky had been peeled off the heavens and placed around Shadyvale.
To a certain extent, this was true in that Rorona had crafted the stone to become a massive magical well, an artifact that drank magic directed towards it and the area around it like the night sky drank the light of a bonfire, like the light of the //stars//. Mortal magic can barely touch it, of the works of mortals only those paid for in blood and iron can hope to scratch the surface of the fortress. It will take the magic of the gods to overwhelm it.