Monoliths

Monoliths are mechanisms that change the background to a Celestial Tower background. They can be activated via right-click, or via wire. There are four different Monoliths, all of which are crafted from the Ancient Manipulator, for 15 Celestial Fragments. The Monoliths make the nearby surrounding area their respective color, with Vortex being green, Solar being orange, Stardust being blue and Nebula being purple. Monoliths have a range of 70 blocks.

Monoliths do not stack their effects. Only the one placed furthest to the right will affect a given area. They do provide large amounts of light in the area they're activated in, which can be useful for solar eclipses, for example.

Trivia

 * If a Monolith is left active when exiting a world, the background will remain when selecting a character and world for single player. Exiting the game returns the background to normal.
 * The Monoliths appear to be miniature versions of the Celestial Pillars.
 * When used during a Blood Moon it will override the red tint.