This is set during the Hogwarts Express Ride with Harry's children are heading to Hogwarts as seen in the last scene in the Deathly Hallows...

Harry, Ginny and Lily return to their home only for Harry to be called to the Ministry an hour later.

An unknown group of Dark Wizards have attacked the Hogwarts Express and the Aurors respond.

There is a brutal battle between the Aurors and Dark Wizards but the Aurors win at last, but half the children are dead and almost all others have been tortured in some way.

Both of Harry's children are dead, showing signs of extreme torture before death.

Harry becomes obbsessed with hunting down these Dark Wizards and after a particulary brutal duel that ends with Harry killing the other wizard so a few days later does he come home to his house in ruins and both his wife and daughter tortured/raped/killed and this push him the final way into darkness.

Soon after he is fired from the Aurors because of his brutal methods in hunting down the Dark Wizards.


Rules:

Harry must be dark. If he becomes a dark lord and gathers followers or remains alone is up to the author.

Ron and Hermione must join Harry but Hermione must have at least partly joined to try and stop Harry, when she knows that there is no stopping harry does she leave but Ron remain.

Draco Malfoy has not really changed, he is secretly supporting these Dark Wizards with Money and Information.

 

Well, this is basically post-DH Dark!Harry 101. Not so much a plot, as the only way to turn Harry dark after the pussified ending of the series.

 

Wasn't a challenge almost identical to this one (but much more elaborated) posted not so long before?

Still, I don't find it all that bad.

Meh, seems that we are before the birth of a new genre of HP Fanfiction...

 

Find something a bit more creative. After twenty years of living with Gin-Gin I doubt Harry would have the balls to go dark.