Anastasius was a planet from within the Unknown Regions of the galaxy, and existed as one of the last creations―along with Vyselennaya―of the World Builders, an ancient species known as the Xaxax. At some point, Anastasius was believed to have been associated with the ancient Gree Enclave, due to the presence of a Hypergate that linked the planet to Ilos, which was situated on the far opposite end of the galaxy.
Eventually, Anastasius became associated with the Brotherhood of Sicarius. As revealed by the exiled Dervish, Xaga Terron, a family of Miraluka resided on Anastasius that produced many elite Dervishes of the Sicarian Order. The terrain of Anastasius was described as cold, barren and soulless metallic environment. The only significant structure known on the planet was the Kaestellium, a massive labyrinthine citadel. The Hypergate was stated as being located within the Kaestellium.