How not to Cage

Humans had been at war with demons. Flesh eating creatures that had magic and technology more advanced than that of fae. Hope was lost.

When suddenly, the portal linking the Demon realm to earth mysteriously shutdown five years into the war, having all the demon soldiers expelled. Seemingly the doing of the Earth king

Enraged, the demon Emperor swore to go down to Earth take over himself when the portal opened again. Through out the realm there was no greater terror than the wrath of the demon Emperor.

What happens when the Earth king gets expelled from Earth alongside the demons into the demon realm, as a consequence of shutting down the portal?

What happens when the demon Emperor comes face to face with his enemy of five years, the Earth king, who was far far away from his safe abode and in the territory of his kind's worst predators?

What happens when the Earth king, is not really a king, but a queen?