Dark Sirius

Dark Sirius was a planet mentioned in the musical Ai no Sanctuary. It was the third planet of a system somewhere in Orion which apparently had no sun. A group from Dark Sirius, led by Dark Nibiru, came to the Earth with the intention of taking the Silver Crystal in order to make it their sun; they believed that the crystal was one they had lost on Earth centuries ago, and therefore it should belong to them.