Concept 3
Unwilling Accomplice
Abernathy's POV
Threats of punishment couldn't keep him in line. There were too many outbursts. Too many slip-ups. Silent shows of rebellion; of eye-communication with the war hero; of wooing Credence away from the tangled path. After the third time their plans were bungled and a stray spell took out Campbell permanently, Abernathy proposed an alternative solution. One menial side-trip to New York, to procure an unlikely quarry.
They didn't have much trouble after that.
He still fought them. Mentally, forcing Queenie out of his mind one moment, crushing her with despair and agony the instant she relaxed her guard. Instinctively, balking at every hand on his shoulder or whisper in his ear. Subtly, incapacitating where there should have been a kill, or bringing down an entire building that buried himself while his quarry escaped, claiming innocence with such adamant fervency that Grindelwald stayed his hand, while Abernathy screamed that he was playing them all along. Physically, when he could get away with it, shoving at the hands that forced him to kneel, ducking away from the dark lord's condescending gaze, clinging to the bars surrounding his muggle friend until they bruised his fingers and dragged him away from the cellar. Silently, projecting every flicker of hatred, fear, and desperation with his sad, weary eyes, until Nagini proclaimed that she could not stand to be in the same room with a trapped animal.
They curbed his outbursts wherever possible, learning how far to push before he was useless. Hunger kept him moving. Sleep was granted in short bursts when necessary, to sharpen his mind. If Grindelwald was feeling generous, he was allowed to see his friend. There was a case - not quite as effective, for the real one had somehow been hidden away before they captured him - but Grindelwald knew how to mimic galleries and he had his own collection of mistreated, bedraggled monstrosities tucked inside a black valice, which the magizoologist was allowed to tend, knowing that if he messed up badly he would find one of them crumpled inside, bloody and snarling in its death throes.
Yet with all these safeguards, Abernathy knew it was only a matter of time. While the war hero lived, there was a chance. Only one wizard could convince the prisoner to risk all and give himself up, to be obliviated or tortured or locked away in Azkaban, just so that he would not have to hurt the one he loved dearest. While this guardian survived, all might be for naught.
Grindelwald dreamed of a warrior who would kill kith and kin for the sake of a friend.
Abernathy knew better.