Zettai madžú sensen Mesopotamia ⅠⅠ (E20)

Tiamat falls into the underworld, but there, she transforms into one of the Evils of Humanity: Beast II. Hassan-i Sabbah, the first Old Man of the Mountain, intervenes, using his power as Grand Assassin to deprive Beast II of her immortality. Seeing their chance to finally destroy Tiamat, Fujimaru and his companions attack. However, Beast II manages to evade them and begins to climb out of the underworld! Her ascent, though, is thwarted... (Crunchyroll)