It will be someone you know, but you won't know it when you first see them. You will have to unravel it over time. It sleeps inside them like a stone in the heart of the earth, vibrating endlessly, aching to(more) thrust itself through the stratum and into our world.
When you see that person for what they are, do not hesitate.
Some find it hard to claim the bargained life when the time comes. The flesh will be familiar. Perhaps it will even be someone you love. From the outside, they will seem in every way as if this damned endeavor had never been.
But whoever they were at their core died when you brought this burden upon us.
All that's left is a husk of flesh, with a sleeping abomination wrapped up inside it. Anything you think you may have shared with them was like a secret spoken through a wall into an empty room.
This was the bargain you made. You may feel aggrieved when the time to pay arrives. But remember-- at no point did we coerce or mislead you. Top to bottom, front to back, you chose this path all on your own.
We even allowed you other walks of life, second chances-- and you chose to return here, because you found them wanting. You gave all of them up in exchange for the power we've granted you.