Gates of Helgallen

I am the creator of worlds.
I create, it's what I do.

The gates of Helgallen rose high up into the sky. The gates that were meant to keep away all evil and yet, only replaced it.
The gates that had been built. The gates that were made of ages themselves. Ages of dedication.

There is not one left who knows who made them. 

The gates were supposed to keep away otherworldly evils. Yet, no protection is ever perfect. Eventually one creature got through. It helped other creatures through the gates and amassed an army that way. The evils were set loose on the world and now they control it.
The only way to escape this world is to escape through the gates to the void where the evils came from. However, this is prevented by those same gates and the devils guarding them.

The gates that used to protect the world are now a tool of the evils.