Nebula Brick

Every fragment you turn into brick is a fragment not going into armor or a wing set, so in practice this is a post-endgame material. Once the lunar events are something you farm for entertainment, the price stops mattering and a single invasion yields enough for a whole room.

It gives off its own light, which is the real reason to use it. A floor or wall of these removes the need for torches in a build where torches would spoil the look. The pink glow is strong enough to tint everything nearby, so it works better as an accent stripe than as the main material for a large hall.