Theseus and Graves become Grindelwald's right hand men. They were disillusioned with the current system and Grindelwald convinced them to choose a side in the upcoming war. Their aurors kept loyal to their bosses who have been hard but always fair on them. Tina and Queenie are among them.
The only loose thread left before starting to take over is Theseus' beloved younger brother and leading magizoologist Newt Scamander. Grindelwald and Graves seduce Newt to their side.

+ dark fic but not relationship-wise...I want to see Graves and Grindelwald make an effort to woo Newt (e.g. by bringing him endangered creatures).
++ Grindelwald looks like Mads Mikkelsen.
+++ Credence lives and is Graves' protege.