Astaroth

Astaroth (アスタロト) is the true Demon King of the Demon Army and the ruler of Gehenna, the demonic world of which demons originated, often called Hell. He's according to Yasaka, a true threat to the universal stablization and the enemy to the gods such as Aqua or Eris. Instrumentally more powerful then Yasaka, he was sealed by the Primordials during the Dawn Era of the universe, sometime before the, the pre-creation era of the universe.