This is the weapon style Death's Hand uses. As you probably know, it is a unique style. Only a single opponent in the entire game wields it. It is not available from any of the stores and it most definitely will not be granted to you by the plot. This one you have to fight for.
It's well worth it, though. Of all weapon styles Death's Razor does the most damage by far. But be warned: Since this style uses a dagger, the regular attacks have a rather short range. That makes mastering this style a bit tricky. The Power Attack and the Area Attack are quite the opposite, to be sure. Their range is about as good as it gets. But they do have a minor drawback: Their usage costs focus. The regular attacks on the other hand are cost-free.
Weapon Style Slam and Clear Drain Focus These two blades - a dagger and a sword - are the legacy of Death's Hand. The way in which these weapons are wielded is just as unique as the blades themselves. Of all the weapon styles this is probably the most destructive one. Because of the dagger the Regular Attack lacks the range of other weapon styles and can be difficult to master. But the whirling Area Attack and the devastating Power Attack are without equal.
Now, I've heard some say, that fighting Death's Hand was a bit of a let-down. Maybe it was. But definitely not because of his style. The AI simply doesn't know how good it is! :) Try it yourself! It's enormously powerful and quite elegant. It may also be a bit trickier than it looks in this video...