Grindelwald has the real Percival Graves somewhere in a safe house and he has all the incredients necessary for a Polyjuice potion. But assuming a man's identity begins with stealing his face, it doesn't end with it. He needs to know all that can be known about Percival - all his personal and professional secrets. Who he trusts, who he loves, who he dislikes, the cases he's worked on, past successes and fuck ups, even the not-so ethical things he's done and thought about. Every dirty little personal and professional secret an Auror in his position is bound to have.

But how do you go about breaking a man who is specifically trained to withstand that sort of interrogation? Legilimency? Physical torture? Emotional manipulation and blackmail? All of the above and more?

One thing is for certain - Percival Graves might have extensive training to resist torture and interrogation, but he's still a human being. And everyone have a breaking point. When Grindelwald is done, there's very little left of the proud, regal Auror.

Bonus points for noncon used as a tool of torture.