Luminite Brick Wall

This only exists once the Moon Lord is down, so it is decoration for a finished world rather than material you use on the way up. Placed by hand it does what any player wall does and shuts off spawns behind it, which makes it a decent lining for a late game arena you also want to look sharp.

The brickwork lines up with Martian Conduit walls, so you can run the two together and the seam between them disappears. That is the detail worth knowing if you are building anything in the science fiction direction, since it doubles the palette without breaking the pattern.