OOC: I was thinking this for a story:
The DE are after the prophecy in the department of mysteries, but the DE have also been getting rumors of agents going against the DE, so they infiltrate Max's gang. They find out about Max and wanting to get control of hogwarts and Max's gang, they get in Max's head like they did Harry and show her an image of Voldemort with Tony. The DE plan to capture her and use her as bait to draw out the order(and max's gang) and defeat them. Max, believing she can rescue tony,(who isn't really there) and avenge Cedric, sets out and falls right into the trap.
That's as far as I've gotten. I'm not sure how you guys or Harry's group fits into this. The unicorns are part of a ministry attempt to get more control over hogwarts and the surrounding area.