Eldritch MonolithsEditOtherwise known as "Obelisks", are generated structures added by Thaumcraft 2. They float above a 3x3 panel of Eldritch Stone surrounded by randomly generated amounts of different materials dependent on the biome.
Plain, Mountain, Forest, and Jungle Monoliths are surrounded with stone bricks and pillars made of Circle stone bricks.
Desert Monoliths have various different types of sandstone surrounding them.
Swamp Monoliths are surrounded with mossy cobblestone with mossy cobblestone pillars.
The Secret of the MonolithsEdit
If you were to wear the Goggles of Revealing, you would see symbols embedded into the central blocks of Eldritch Stone beneath the Monolith. These symbols are, again, randomly generated. The different colors of the symbols apply to different crystals.
It is possible to place crystals in the four edge blocks beneath the obelisk. You must place the correct crystals in each slot. If you attempt to place the incorrect crystal in a slot an explosion will occur which destroys blocks and damages mobs and the player. When all four crystals are in place the center block will vanish revealing a long drop.
IMPORTANT Use Vis CRYSTALS, not crystal ores.
Be sure to have a safe method down and back up, it is recommended to drop sand down the hole until it is full then digging down, then when you are ready to go up simply place the sand beneath you as you jump up the tube.
At the bottom of the tube there is a small room made of Eldritch Stone with four Void Chests. Some will have Void Interfaces on top linked to random frequencies. Inside these chests are several eldritch artifacts and materials. You may also have noticed the different blocks on the edge of each wall, this is where you place the Eldritch Keystone: Tlhutlh, doing so will unlock yet another room with more Void Chests to open, any Vis Crystals that were in the area will be dropped within when the room appears.