Our realm has always been split into two: 
Those from the old world.
And those from the new.

When a deadly and magical plague created yet another caste in our realm, those of the new world thought it a punishment from the gods for their destruction and abandonment of their roots, but those in the old world knew the truth.

That was to be the beginning of a long and drawn out war between creatures that have roamed the realm for centuries and monsters that never should have came into being.