Monoliths are 困难模式, post-Lunatic Cultist 机构s that change the background to their respective 天界塔's background when active. They can be activated via right-click, or via 电线. There are four different Monoliths, all of which are crafted from the 远古操纵机, for 15 Celestial Fragments. Monoliths have a range of 70 物块s.
Monoliths do not stack their effects. Only the one placed in the spot furthest to the bottom right will affect a given area. They provide large amounts of light in the area they're activated in, which can be useful for situations in 事件s like the 日食.