The Line Is Thin

The world is full of things we cannot see, full of new colours and scents and dimensions mankind will never fully appreciate. It is said that once humans reached towards darkness it answered and the line was never fully closed - quite the opposite. The veil between this world and the next is wearing thin and gets thinner every time humans reach for more. All the darkness had to do is wait.
According to the high mages, there is one exact location when this tear in the fabric of reality can actually be seen. This secret gets revealed only to the most skilled people of the order, as thorough the centuries, the mages tried anything they could think of to try to close the gap or at least minimise it. Since the gods have left, they see it as their duty to try to mend the world of the mankind's original sin.
From time to time, creatures and shades manage to escape through the tear, and those who witness the carnage they are capable off, never wish to know what would actually happen if the world trully opened up to what is lurking beside it.
So far, there is no actual remedy known and the nobles are unsure whether to be more scared of the darkness or of the very first mage who succeeds in surpassing the known gods, should their spells be ever successful.