Underworld.

Currently Sirzech is busy convincing his devils of the Dark Forces threat when suddenly demons strike completely surprising everyone as they never saw these demons before.

However despite the devils superior to magic they are losing against these demons as they are absorbing their attacks.

Even the supposed four Great Satan's are having a difficult time against these demons like Malladus who is easily blocking the four great Satan's powers.

Malladus: "Fools! This underworld shall be the domain of Demons! Especially to the Demon Lord Ghirahim!" He said then unleash a blast that completely vaporized multiple buildings.

Serafall: "The Underworld belongs to both Demons and Devils! Why must we fight?!" She said as she prefers peace over war.

Only for Serafall to freeze as she sees a giant shadowy whale in the sky which caught everyone's attention.

Malladus: "Ah well Bellum it seems you finally arrived" he said then a giant skull knight appeared.

Bellum: "It took a while but I managed to bring my forces but to answer the false Leviathan it is quite simple. We demons deserve to rule but you devils treat us like we are weaker! Well no more for the Demon Clan and all demons will claim the Underworld as our own!" he said then both Malladus and Bellum combined their powers to vaporize countless devils thus forcing the remaining devils to retreat to earth.

Then Ghirahim appears as he uses his magic to transform the ruined city into a kingdom.

Ghirahim: "The Underworld belongs to the Demons!" He said looking at his fellow demons which the demons roared in victory.