A useful item that let you see light levels.

It was crafted with amethyst and iron and displayed the light level with a bar on the front.

It was removed as light levels became mostly irrelevant due to the change making mobs only spawn in complete darkness.

History

1.0.0X

This feature allowed you to see what mobs could spawn in the block you were standing in, based on the level of the bar shown on its display.

Does that sound confusing? Because it totally was. This feature was useful, but thankfully Mojang made it obsolete by preventing mob spawning in any areas with even a minimal amount of light.