Companion hollows are new hollows that form near a current hollow. This can happen due to high Ether activity in the area.
A companion hollow formed by the Lemnian Hollow. Researchers believe this was caused by the collision of two high-intensity Ether energies.
A new Companion Hollow of the Lemnian Hollow appeared at 6:30AM today. The diameter of the new Hollow is still being calculated, and its expansion is gradually slowing down.
Discussion of the Lemnian Hollow in Ridu's Newsletter Vol 3