Two beings capable of using magic. Obsidian mostly uses fire, but may also use shadows or stars to attack his enemies. Aster is connected to the Underworld, and uses powerful (in some cases, dangerous) magic with the help of souls. It may sound strange, but Athanatos is actually Aster's father. And you may be wondering "How did Aster start existing if Athanatos never had a girlfriend?", and the answer is: he used magic (and some of his own Stardust Syrup) to create a creature that slightly resembles Athanatos himself.
Art+OCs: @Duskdawn06 Audio: Nightmare Tower, Stage (Miitopia)