Delta Clan consists of witches, demons, and vampires. Only the Delta Clan has the ability to conjure a soul from the dead. Supposedly, during the time of Aurora Borealis, Crux Australis and the other hellions were summoned from the Demonic Realm and were placed in clay bodies. The clay bodies would become real when the soul enetered them. However, ancient techniques were lost and it became more efficient for modern day scientists interested in reviving souls to use the mechademons instead of the clay bodies. They can place it inside of the body of a mechademon which happens in Volume 4.
Pluto Australis has an extremely sought after gift for reviving the dead. No one has had a power like his since the time of St. Aurora Borealis when a witch was able to pull souls from hell to create the Hellion Army. He never uses his gift unless someone he loves is threatened. He spends most of the series as a good character working as a double agent between the hellions and clan leaders.
The Australis Family is the largest family in the Delta Clan. Pluto is from a minor family in the Delta Clan. Pluto became a part of the Australis Family because of his arranged marriage with Orcus. On Dionne, it is natural for men to take on the surname of the women especially if the woman is from a family that is higher in rank than the male's family. In this case, Pluto took the name of Orcus Australis. Pluto came from poverty and Orcus is the extremely wealthy heir of the Australis Family and a prized descendant of Crux.
During the time of St. Aurora, Queen Corona Borealis was killed by Crux Australis, the Demon King. For generations afterward, the Australis Family boasted about ending the Borealis Family's chance at having a royal lineage. It wasn't until Uno Borealis married the prince that the Borealis Family had another shot at a royal lineage. In other words, it took one thousand years before the Borealis Family married into the royal family again.