Item Cage is a unique block found in the four corners of the puzzle room in the Wight Fortress. It is key to the assembly of the Shockwave Sword. They as well as the energy orb they create give off a blue glow using the mod's shaders.
The Puzzle Edit
The center room of the third floor of the Wight Fortress is a special puzzle room, featuring Spike Traps on the floor as well as the four Item Cages directing energy beams towards the center orb of the room. Each of the Item Cages contains a piece of the Shockwave Sword. The idea is that you are supposed to break all four Item Cages (ONLY done by breaking them while standing directly underneath them) while maneuvering around the Spike Traps. The released pieces will float towards the center orb and, once all four are united, the orb will disappear and leave behind the Shockwave Sword.