This story is good so far. The chapter length is okay and the character and plot devolpment has been done well.
It is also nice to see a different idea coming forward, many people would not think of cross over like this.
It will be interesting to see how you develop Harry into an Overlord.
I must ask though...
Who will be Harry's mistress?
And if you still need a Beta then I would be more than willing to help as I do have knowladge of writing a Dark Harry from reading other stories. I am also fairly familiar with the plot of Overlord.
I hope you enjoy writing this fic, as much as I enjoyed reading it.
As far as I have things planned, the Mistresses will be Luna Lovegood, Fleur Delacour,and that Hermione Granger. I already have a beta, though I appreciate the offer, and you can rest knowing that Harry's evil transformation will take quite some time. He will become Evil by the end, though.