Fate/Zero Promo!!

And epic background music is EPIC. And dark. Not to mention how it just screams KAJIURA(-SAMA). Sounds a lot like Tomaru Hanae on lead vocals, but I could be wrong.

Oh yeah, the animation is really gorgeous too. I'd expect no less from ufotable. Like with most made-for-TV anime the animation standards will probably falter as the series goes on, but this is a pretty good upper limit.