Soul Monger

The practise was ancient. And profitable. For centuries the Soul Mongers crossed the mysterious Transcender portal that linked their universe to ours. Their mission?
Whole souls.
The name they gave to humans.
But it was only in the Soul Monger's universe our remarkable potential could be fully realised; only there did we learn just how truly unique we are.
And how prized we would become.
As slaves.
In time, an enlightened and benevolent League became the symbol of a new order and many systems and worlds were drawn to a new awareness. Trade and commerce between the Treaty planets flourished and slavery was outlawed. With the Transcender sealed and denied their secret access to our world, the Soul Mongers and their vile trade all but died out. The legends of whole souls faded into history.
Until an unnamed enemy rose, waging a fierce and merciless onslaught the peaceful League were powerless to withstand, unless they once more acquired the deadliest weapon known to their universe.
Us.
And only the very last of the Soul Mongers knew where we were.