Location: Bahro Cave, Relto
These four pillars are first found in the blue Bahro Cave. We are not entirely sure what they do, but according to Yeesha, they are tied to the very soul of the Bahro. Touching the Journey symbol on the wall beside the pillar will transport it to your Relto. In order to complete Yeesha's Journey, you must return the four pillars to the orange Cave above the Rudenna Cavern, and the Bahro will return to D'ni.
Somehow, the Bahro Pillars are connected with Relto and the Star Fissure. Returning them to the orange Cave will make the outline of the Fissure appear, and removing all four will bring an earthquake to Relto, opening the starry expanse.
Note that when in Relto, the Pillars have a blue-gray mist coming from the top, and glow less often than when in one of the Caves.