Solar Brick

Fragments are the same currency as your endgame armor and weapons, so a wall of these is a statement that you are finished gearing. Once you are past that point they are the cheapest good looking block you own, since the Pillars keep handing you more every time you run the event.

It gives off its own hot orange light, so a room built from it needs no torches and lights evenly instead of pooling around a fixture. That suits a forge or a hellish tower. It fights with almost every other palette, so commit a whole room to it rather than sprinkling it around.