Also, headcanon time: the dagger was intended to be a sword, but the blade snapped in the forging process. Because they couldn’t just re-melt the heavily enchanted metal, Shedalsky had the smiths turn the blade into a parrying dagger.
It’s based off the flamberg, a French blade pattern. Though it was historically used for all kinds of swords, today it’s associated with two-handed greatswords.
The advantages lies in the fact that it hits with a smaller surface area, and that dragging the blade along the opponent (called a pull-cut) caused more damage. It also displaces the opponent’s blade more when hitting it with the edge.